Of Bytes and Borders

There is more to the screen than those pixels or tiles which a graphics programmer had the ability to manipulate into graphical images.  In many vintage consoles and home computers, their display hardware could sometimes display color outside the active display area.  In this blog post we will review some of these devices, try to identify the size of the borders and any special purposes to which they may have been put.

StarTech USB3HDCAP Review - A Jack of All Trades?

The StarTech USB3HDCAP (courtesy of Amazon.com)

Capturing real hardware has always been something of a challenge, especially when it comes to retro video game consoles and computers.  I have been seeking an affordable "all-in-one" capturing solution for some time.  Recently I read about the StarTech USB3HDCAP and remarked that it could handle odd inputs like 15KHz RGB, 240p Component video and even 320x200 70Hz VGA.  I also read that the StarTech uses the same hardware as the more expensive Micomsoft X-CAPTURE 1 and the less-featured Elgato HD60 S.  I purchased a card recently and found that getting the best out of it is not quite as straightforward as I expected.  Here let me discuss what I have tried and how well it works.

The Rise of Interlacing in Video Game Consoles

Until the Genesis and the SNES, all video game consoles used 240p resolutions.  However, in the quest to gain greater graphical detail without severely impacting performance, game programmers began to use interlaced video modes in the fourth and fifth generation of video game consoles.  Then in the sixth generation, interlacing was the norm and progressive scan was the option.  By the seventh generation, HD gaming was the norm and interlaced graphics usage was more or less here to stay.  Let's explore the issues surrounding interlaced video game graphics here.

The Realistic Portavision - Portable Television in the 1980s

About a week or two ago on this blog, I may have foreshadowed that I had acquired a new electronic item worth talking about.  Portable televisions have always been of interest to me.  Since TVs became mainstream in the 1950s, marketers have always tried to find ways to make TVs smaller and able to be used in more and more places across the globe.  My little acquisition represents the peak of its technology for its time, so let's look at it in greater detail.

The system in question is called the Realistic Portavision.  Its most notable feature is that it is a fully portable color CRT TV.  A sticker on the back of the unit stated it was manufactured in November of 1985.  During the 1980s, portable TVs were not particularly rare.  Many kitchens and campers featured one.  But these TVs were typically black and white TVs.  Black and white TVs were much cheaper to manufacture, required fewer components to make them work and consumed less energy. Black and white TVs in portable sizes were quite common by the mid-1970s and were manufactured throughout the 1980s.

YouTube Playthrough and Demonstration Series

This Christmas, I got a capture device.  The device in question is an I-O Data GV-USB2.  It can accept composite or s-video input and has stereo sound inputs.  The manual is in Japanese but the drivers are in English.

One of the reasons why I acquired this device is because I found a disturbing lack of video game footage captured from real hardware on YouTube.  While there are plenty of playthroughs or longplays of various games, many of these are from emulators.  Footage directly captured from consoles tends to be older and is reduced to 30 frames per second.  The heyday of 480i/30 frames per second was the Playstation 2 era.  Before the Playstation 2 and the Dreamcast, it was not often used and almost never used by the SNES or Genesis.  They used 240p and ran at 60fps.  So did many vintage computers from Apple, TI, Commodore and Atari.  Even 320x200 256 color VGA graphics is just double-scanned 240p.

As many people know, 240p is a hack of 480i.  TV tubes were designed to display 480 interlaced lines 60 times per second (in NTSC countries).  The odd lines of an image would be displayed, followed by the even lines of an image and your eyes would see fluid motion.  30 times per second the TV would be drawing odd lines and 30 times per second the TV would be drawing even lines. 240p works by telling the TV to odd lines always, 60 times per second. Because the even lines are never being drawn, there is a space between the lines which can be noticed at times as scanlines.  The console or computer is sending a complete frame for the TV to draw on the odd lines.

Recovering 240p from Video Capture Devices and Putting it Online

Video capture devices are often used to backup NTSC video sources like VHS cassettes and DVDs.  Many consumer level devices on the market have this purpose in mind.  You can use these devices to backup old video recordings, unprotected commercial video tapes and DVDs.  Your retro consoles and some computers also output an NTSC signal, but there is a substantial difference between the two.

Your standard NTSC-M video source uses a 480i resolution.  The picture is constructed from two fields, each containing half the data of a frame.  These fields are interlaced so that the odd lines of the frame are displayed first, then the even lines of the frame.  The eye usually cannot notice the interlacing effect when viewing a CRT TV screen at a reasonable distance.   In NTSC, there are 59.94 fields displayed in each second, half odd, half even.  This gives an actual frame rate of 29.97 frames per second.

All consoles from the Atari 2600 to the Nintendo 64 typically output 240p video.  Many computers, including virtually all the 8-bit home computers from Apple, Commodore, Atari, Texas Instruments, Timex Sinclair, Mattel and Coleco output 240p.  Some more advanced home computers, like the IBM PC with CGA, the IBM PCjr and Tandy 1000, the Atari ST, Apple //gs and Commodore Amiga also can output a 240p signal.  All these hardware devices output 240p do this by tricking the screen.  Instead of sending the proper signal for an odd and an even field, they send the signal for two odd fields.  The resolution is reduced to no more than 240 lines, and often there are fewer visible lines drawn and the rest of the lines are filled with a background color, often black.  On the positive side, the images are drawn twice as frequently, 60 times per second.  Because the screen is not evenly covered, scanlines are more visible in 240p than 480i.  This was not part of the NSTC-M standard, but works on every NTSC CRT TV and monitor ever made and most LCD monitors and TVs that could accept a composite input until recently.

The Amstrad PC-1512 : The Affordable IBM PC Compatible for Europe

The Amstrad PC1512, What you See is the Hardware you Got (credit to wikipedia)

In 1986, Amstrad released the PC-1512 for in the United Kingdom.  Amstrad was a leading manufacturer of home computers, having launched the successful CPC series and by 1986, having bought Sinclair Research and would release more computers in the ZX Spectrum line.  However, both the CPC and Speccy's were known more for and better at playing video games than serious work.  Unfortunately, the standard business computer of the day, the IBM PC and clones, was very expensive.  The cost of a minimally configured PC compatible or clone was well out of the price range of most European consumers.

Neither of Amstrad's key computer lines were IBM PC compatible so Amstrad decided to design their own PC Compatible.  The solution they came up with was innovative in many ways but a bit limited in others. Enter the PC-1512.

The Amstrad PC-1512 uses an 8086 CPU running at 8MHz like the Tandy SL, SL/2 or the IBM PS/2 Models 25 & 30, but it came earlier than either machine.  The CPU is in a socket, so it can be upgraded to a V30 for increased performance.  The stock system came with 512KB of parity memory, which was very reasonable for a low cost PC clone at this time.  (The Tandy 1000 EX and HX came with half that and the SX came with 384KB, all non-parity).  The RAM can be upgraded to 640KB with eighteen standard 64Kx1 DRAMs, 150ns or better.  It also has a socket for an 8087 Math Coprocessor and a built-in floppy controller with DMA.

The PC-1512 came with one or two half height 5.25" drives, and in this regard looks very similar to a Japanese NEC PC-8801 or 9801 machine.  The keyboard is based off the IBM 83 key keyboard with many improvements to the layout.  It has 85 keys and looks like an IBM PC AT keyboard. Apparently the PC-1512 was released in the United States, but it was not popular.  Likewise, the Tandy 1000s were released in the U.K. and Europe, but were not popular.  The US and UK keyboard are almost identical and the UK keyboard is rather US friendly in terms of key layout.  The keyboard is not compatible with any IBM-compatible keyboard, but there does exist at least one compatible 102-key keyboard.  Early Northgate Omnikey keyboards also have Amstrad compatibility with a special cable.

Input was also very innovative for the time.  The system came with a mouse out of the box, which was always a separate purchase for other IBM PC compatibles of this time.  The Amstrad mouse is extremely ugly looking, even by the miserable mousing standards of the 1980s. It looks like the designer was inspired by the Moai statues of Easter Island.  You should be able to build an adapter to allow a bus mouse which sends pure quadrature signals to work in the PC-1512.  I believe an Atari ST mouse may also be compatible.  I'm not sure about an Amiga mouse.

Expansion is pretty decent.  There is a standard 25-pin serial and parallel port on the back and three slots inside the machine for ISA expansion cards.  The keyboard connects to the machine via a 6-pin DIN.  Next to the keyboard port is a DE-9 mouse port.  The mouse is a proper rotary optical mouse, but the two mouse buttons are redirected to the keyboard port.  The keyboard will report the mouse buttons as otherwise unused raw keyboard scancodes.  Of course, with the proper mouse driver, this should be transparent to the user.  If you want to assign the mouse buttons to a particular keyboard key, you have that option.

Even more interesting is the Amstrad joystick, which attaches to the keyboard via a DE-9 port.  The joystick pinout is compatible with standard Atari joysticks, but also can support a second button on pin 7, which is not particularly standard (Genesis and Master System controllers use Pin 9).  This is a digital joystick, which is a first in the PC world.  The keyboard treats the joystick simply as six extra keys, giving a unique raw scancode to each key.  The built in firmware translates the joystick directionals to cursor keys but the buttons can be user defined to produce the translated scancode of any key.  The Amstrad can also use a standard IBM PC compatible analog joystick with a standard Game Card or a Sound Card.  This feature was carried over to the PC-1640.

Like the Tandy 1000 EX and SX, the Amstrad has a volume control for the internal speaker.  The dial is accessible outside the machine, like the EX.  The SX's volume dial is inside the machine, an issue fixed with the TX and HX.  There is no additional sound hardware outside the main PC speaker unless you add a sound card.

The Amstrad came with one or two 5.25" 360KB drives.  Upgrading the drives to 720KB can be done.  The data separator in the PC-1512 cannot handle the 500kbits per second speed required for high density drives.  In addition, Amstrad drive cables are untwisted, so you will need a way of setting a modern 3.5" drive to DS0 instead of DS1 for the A: drive.  You do not need to do anything for the B: drive in this case. Installing a hard drive into one of the bays was a standard, if expensive, option.  You would need to add a hard drive controller card into one of the expansion slots or use a hard card.  The Amstrad can accept a 13" expansion card, unlike the Tandys.

The Amstrad had a built in real time clock and CMOS RAM.  It is a standard HD146818 like the one used in the IBM PC AT and powered by 4xAA batteries instead of coin cells, barrel batteries, or the Dallas Smartwatches.  The CMOS setup is pretty basic, but is used to assign the number of disks, starting text/graphics mode, initialize serial port parameters and can be used to assign a keyboard translated scancode to the joystick and mouse buttons.  Tandys of the time required an upgrade for a RTC, either being fitted underneath a ROM chip or on an expansion board.

Most PC compatibles had a fan for the power supply.  Early PC1512s did not come with a fan, even for the power supply.  The reasoning was that the inclusion of the power supply in the monitor allowed for adequate cooling by natural convection.  However, when rumors of unreliable machines popped up, Amstrad put in a fan.

The Amstrad came with MS-DOS 3.2 and Digital Research DOS Plus, the latter of which can run MS-DOS or CP/M applications but was slower.  It also came with DR's GEM graphical user interface and the GEM Paint program.  The Paint program supports 640x200x16.  Tandy provided something similar with its Deskmate II software with the SX, but Deskmate II gave only a text-mode based interface.  The EX's Personal Deskmate used a true graphical interface but it was fairly limited.

The 1512 has a special CGA-style monitor.  This monitor comes in monochrome and "colour" varieties.  This monitor is unique to the 1512 because it provides power to the system unit.  No monitor = paperweight.  The monitor provides power to the system unit via a very unusual DIN-14.  The system unit provides video to the monitor via a DIN-8.  This DIN-8 combines H-sync and V-sync on one pin, standard CGA separates the H and V signals into two pins.  The signals for the R, G, B, & I signals are still digital.  The Amstrad does not have composite CGA output, so the monochrome output is digital and uses 16-shades, giving sharp and distinct image quality.

CGA compatibility on the 1512 is nothing to write home about.  The standard BIOS-compatible CGA modes are supported as is the 160x100 "graphics mode" and the alternate cyan/red/white palette. Composite color is not supported because the PC-1512 was designed in and marketed mainly for PAL countries and CGA composite color was NTSC based.  The MC6845 is only emulated and the emulation is not 100% compatible.  The built-in CGA cannot be disabled, so EGA and VGA will be limited to monochrome modes.  A Hercules or MDA card will work alongside the Amstrad's CGA, but you will need a separate monitor.  A Hercules InColor card will also work to provide high resolution color output, but little software supports it.

Amstrad CGA has two or three text mode fonts built in, selectable by a jumper on the motherboard.  Normal/Codepage 437/English is the default, Danish is also available as is Greek on later 1512s.  More important is its 640x200x16 graphics mode.  This graphics mode is unique to the 1512.

However, few games ever took advantage of this high resolution graphics mode.  MobyGames indicates that 21 games support Amstrad graphics, but this does not mean these games support the 640x200x16 Amstrad graphics mode.  The Lemmings games do not.  Iznogoud does not, nor do the two Passenger on the Wind games.  While they do have Amstrad selections, I believe this is to ensure compatibility with CGA graphics, not to implement extra color.  Almost all of these games support EGA and sometimes even Tandy or VGA.  All of these games  come from European publishers and except for Lemmings they are very obscure by US standards.

The one commercial game that has been known to support Amstrad 640x200x16 graphics out of the box is Frank Bruno's boxing.  It gives more color to what would otherwise be 640x200 B&W CGA graphics.  Unfortunately, the game is an unlicensed clone of the Punch Out arcade games and is pretty terrible.  Ironically, it does not support the Amstrad joystick.  Here are some screenshot comparisons :

Title - Amstrad

Title - CGA

Opponent Profile - Amstrad

Opponent Profile - CGA

Fight - Amstrad Colour

Fight - Amstrad Monochrome on Colour Monitor

Fight - CGA

The 640x200x16 mode's implementation is unique to the Amstrad PC-1512.  Its successor, the Amstrad PC-1640, has built-in EGA graphics in place of the PC-1512's graphics controller.  The 16-color PC-1512 graphics mode did not receive BIOS support.  Neither did the 640x200x16 mode with the later Tandys.  It requires 64KB of RAM, but the controller only provides a 16KB window into video memory.  In this 640x200 mode, the window is assigned to one of four 16KB bitplanes, with each bitplane representing one of the four RGBI components.  You select each bitplane then write that component's bits.

On top of this, the Amstrad's CGA graphics may be the slowest graphics adapter of all time (next to the PCjr.)  Topbench's benchmarks show the speed of the Amstrad as significantly lower than a CGA card in an IBM PC or the Tandy graphics adapter in an Tandy 1000SX.  Given that you cannot disable the built-in graphics, you are almost always stuck with slow 4-color CGA graphics.  The Technical Reference states that the CPU has wait states inserted when accessing video RAM to maintain synchronization with the graphics controller and the number of wait states (12-46) seems rather high.

One thing I had forgotten about until writing this article was that Sierra offered support for the 640x200x16 mode in its SCI0 and 16-color versions of SCI1 games!  With a driver called PC1512.DRV, you could obtain a proper, effective 320x200x16 resolution in Sierra's games.  In order to achieve this, each pixel is written twice horizontally.  This driver rarely can be found with the actual games themselves, but here is a place to download the driver : http://sierrahelp.com/Patches-Updates/MiscUpdates.html  The SCI games run a tad slow on the PC1512.  As far as AGI games go, there is no Amstrad driver and you are limited to 4-color CGA at best.

Price and Feature Comparison with the Tandy 1000SX

Amstrad PC-1512 US Prices
Monochrome Monitor Single Drive : $799
Monochrome Dual Drive : $899
Color Single Drive : $999
Color Dual Drive : $1,099

Source : http://www.old-computers.com/museum/computer.asp?c=183

Tandy 1000SX US Prices :
Tandy 1000SX Dual Drive : $1,199
VM-4 Monochrome Monitor : $129.95
CM-5 Color Monitor : $299.95
Digi-Mouse : $99.95
Digi-Mouse Controller/Calendar Board : $99.95
PLUS RS-232C Option Board & PLUS Upgrade Adaper Board : $94.9

Source : Tandy Computer Catalog RSC-17

So, in order to get the functional equivalent of the Amstrad's Color Dual Drive features (except for CPU and RAM), you would need to spend $1,793.75 at Radio Shack on the SX.  Of course, you could often find Tandy options cheaper elsewhere.

Here is a spreadsheet comparison between the two dual drive systems :

Feature	Amstrad PC-1512	Tandy 1000SX
CPU	8086 @ 8MHz	8088 @ 7.16/4.77MHz
CPU Upgrade	V30	V20, 286 Express
Coprocessor	Supported	Supported
RAM	512/640KB parity	384/640KB non-parity
Keyboard	85-Key	90-Key
Parallel Port	DB-25	Card Edge
Serial Port	DB-25	Upgrade
Real Time Clock	Built-in	Upgrade
Mouse Interface	Built-in	Upgrade
Volume Control	External	Internal
Sound	PC Speaker	PC Speaker + Tandy 3 Voice
Expansion Slots	3	5
Video	Amstrad Enhanced CGA	Tandy Graphics Adapter
Drive Bays	2 x 5.25”	2 x 5.25”
Monitor	Included	Separate Purchase
Monitor Type	Monochrome or Color CGA	Monochrome or Color CGA or Composite
Joystick Interface	Digital, 1 Joystick	Analog, 2 Joysticks
Power Supply	57W	65W
Supplied Software	MS-DOS 3.2, DR DOS Plus, DR GEM, DR GEM Paint	MS-DOS 3.2, Tandy Deskmate II

So, it would seem that Amstrad has more advantages.  But not all things are weighted evenly.

The Amstrad CPU is faster than the Tandy CPU, but the slower switchable speeds of the Tandy makes it more early software friendly.  Moreover, Tandy offered the 286 Express upgrade (at 299.95) that would propel the Tandy beyond the Amstrad.  8086 machines had no such upgrade generally available.  

The maximum amount of RAM is the same, but the cost of eighteen 64Kx1 chips for the Amstrad was probably roughly equivalent to the cost of eight 256Kx1 chips for the Tandy.  

Amstrad's keyboard has a better layout than Tandy's.  The keys are more spread out and areas more clearly defined.  Tandy's keyboard has everything mushed together and the extra keys are seldom used.

Amstrad's parallel port is standard, Tandy's is not and is missing one of the control lines.  The serial port in the Amstrad is a welcome feature, Tandy requires an upgrade that takes up a slot.  Cheap these days, however.  A dual serial card will give you a mouse interface for the Tandy, making Amstrad's mouse interface no longer much of an advantage.

Amstrad's external volume control comes in handy on occasion.  With the SX, you can use the multiplexer to silence the internal speaker and allow the external audio output to output PC Speaker and 3-voice music.  See here : http://nerdlypleasures.blogspot.com/2013/06/ibm-pcjr-and-tandy-1000-sound.html

Music is clearly superior from the Tandy machine, 3-voice music was supported in hundreds of games and usually sounds decent even when the game supports Adlib music.

Expansion slots are typically a wash, you need at least one slot on the Tandy for a mouse interface.  Amstrad will have no problem with Expanded Memory Boards, but there are modern Expanded Memory Boards available from Lo-tech that fit inside Tandys.  Vintage 8-bit EMS boards are overpriced.

The Tandy 1000SX has its power supply built in and you are not tied to two specific monitors.  They can also use NTSC-compatible composite monitors and TVs when nothing better is available.

Tandy's video slaps down Amstrad's video.  Tandy's video is much more CGA compatible and is far, far faster than Amstrad's.  Hundreds of games use 320x200x16 and 160x200x16 Tandy graphics, almost none use Amstrad's Enhanced 640x200x16 graphics.  You can easily upgrade to an EGA or VGA card in a Tandy SX, you cannot in an Amstrad.

The joystick issue is not an easy one.  Some games do explicitly support an Amstrad joystick.  Many games which use cursor keys support it by default.  Games that do not use the cursor keys or games that read raw scancodes from the keyboard will not work with the joystick.  The analog joystick of a Tandy is always supported in any game that supports a standard joystick. An analog to digital joystick converter for the Tandy joystick is now possible : http://www.vcfed.org/forum/showthread.php?44532-Tandy-Color-Computer-Digital-Joystick-Adapter 

A Good Retro Display - 19" Sylvania CRT

The System and its TV (no, there is not an ultra-rare Stadium Events in my NES)

Today, most people see CRTs are little more than space-hogging junk that they have to pay a fee to get taken away.  During a move, I happened to acquire a 19" TV and found it was excellent for classic video game consoles.  In this post I will give my opinion as to why it is so great.

The TV set in question is the Sylvania 19" SRT2119A Color Television.  This TV set is bare-bones and obviously intended for a bedroom, not a living room. The SRT2113A is its otherwise-identical 13" version.  It uses black matte plastic throughout, has six buttons on the front (power, 2x channel and volume, menu), a headphone jack and a mono speaker.  It also has a mono-composite AV input on the front and a coaxial RF screw for an antenna or a cable wire in the back.  The tube is curved but the viewable shape is fairly squarish.  If you look behind the back, you can see a fairly deep conical protrusion out the back that encloses the neck of the picture tube.  

The included remote is very basic, containing only 22 buttons.  One of those buttons is the aptly named TV/GAME button, which switches from the coaxial RF connection (TV) to the composite AV connection (GAME).  This remote is not really replaceable with a generic universal TV remote, I tried using my cable remote for all the Sylvania/Funai codes I could find and it did not work.  Unfortunately, the remote is the only way to operate the TV/GAME input switch.  Replacement remotes are available online, as is the Owner's Manual.  

The menus are easy to navigate.  When menu is pressed, the channel buttons select options and the volume buttons change the option.  The standard picture selection options are available, brightness, tint, contrast and color.  Sharpness is mysteriously absent.  The "GAME MODE" acts to remember a particular set of settings.  Many video games may benefit from boosting the brightness signal whereas TV or Cable programs and DVDs/VCRs may look washed out.  

The TV set also supports Spanish menu choices, V-chip, closed captioning and a sleep timer.  It will shut itself off if it detects no valid video signal (except when set to display the composite AV input) after 15 minutes and will also mute the numbered channels when they are displaying static.  It will tune itself to VHF channels 2-13 and UHF channels 14-69.  It is also "cable ready", so it will tune itself to the standard 125 cable channels.  Included in these cable channels is coverage in the frequency spectrum corresponding to Japanese channels 1 & 2, which RF only Japanese consoles use.  An original Famicom will be received on this TV, but you have to add the appropriate channels, 95 and 96 manually.  Channel 96 looks much sharper than 95, probably because of the foreign RF US signals (from the Famicom's perspective). Also, it is best to turn the TV off or the input to GAME when switching RF input channels.  Otherwise you may only see Black and White graphics and hear horrible and loud white noise.  

Opening the tube can be done very easily.  Remove the screws and then the chassis pulls right off.  The circuit board is very streamlined, so streamlined in fact that I could find no potentiometers to adjust.  Nor could I find adjustment potentiometers for the color guns on the tube's neck.  The only adjustments can be made to the flyback transformer, but there is no need to do that typically.  The main PCB can be pulled out from the tube housing for easy servicing. 

The speaker does its job adequately within its limits.  The headphone jack supports mono output only.  There is an audible and annoying buzz when this TV is turned on and nothing is coming from the speaker.  This may be due to the budget nature of this set or an aging filtering capacitor that should be replaced.   

If I may digress for a moment, back in the late 1980s, Nintendo partnered with Sharp to manufacture a TV set with a built-in Famicom and later a built-in NES.  This is the Sharp C1 TV, and it had a 19" viewable screen.  It was highly regarded for its picture quality because it used an internal composite connection.  This was unusual at the time, most NESes were hooked up using the included RF switchbox.  TVs with composite AV inputs were far from ubiquitous in the late 1980s and early 1990s.  Screenshots taken for magazines often would point their camera to one of these Sharp screens because of the improved picture quality (Sharp lived up to its name here), especially in Japan where the original standalone Famicom was RF only.  Essentially for the time the Sharp TV was as close to the canonical NES or Famicom display as you could get.  The Sylvania TV can produce a similarly bright and sharp picture though its composite connector. Newer CRT TVs like the Sylvania may be a better and certainly a cheaper option compared to the Sharp because CRTs tend to age poorly.

One of the Sharp's excellent but rarely mentioned qualities was its very squarish picture viewing area.  TVs have gradually evolved from spherical viewing areas to rectangular viewing areas.  The earliest TVs were like looking through a porthole, then a porthole with a straight top and bottom and then gradually sets gave more defined corners, flatter tubes and finally the perfect right angle corners of late model CRTs, computer monitors and LCDs.  Because the corners of the Sharp TV were relatively straight instead of curved as seen on many TV sets, you could see more video material in the corners.  Some games like Castlevania use those corners, which will be totally or partially masked off in TVs with more rounded features.  This Sylvania TV does almost as good a job as the Sharp TV in showing you the full NES image, the corners are just a bit more rounded.

Not all CRTs are best for classic gaming consoles.  I have read that some late CRTs with HD (1080i at best) support convert 240p material into 480i.  These widescreen HD CRTs may not work with light guns.  I have a Toshiba with a flat tube and it has some very odd distortion with classic consoles.  Often on the edges you can see the bleed from the border color, which should not be visible.  Due to the odd geometry (these tubes are not truly flat) the border often can be seen on the bottom portion of the screen, making the screen image look trapezoidal.  Perhaps because of the odd geometry or its 3 line digital comb filter, this Toshiba TV has trouble with games that rely on precise CRT timing.  Micro Machines is an excellent example of this issue, but many other Codemasters/Camerica games can exhibit bendy rasters..  Both in the menus and in game the raster will get bendy at places.  On the Sylvania TV, the raster is perfectly stable.  In addition, the baseball game on the Quatro Sports cart and the Linus Spacehead game on the Quatro Adventure cart show a vertical rolling screen on my Toshiba TV at times but a stable screen on my Sylvania.

The Sylvania display has its limits.  It only supports mono sound, so systems with stereo sound support, which includes all fourth generation and later consoles, will not show their true aural potential.  Consoles that can support more advanced video output modes, such as RGB, S-Video and Component Video, will not look their best.  Finally, 19" is not everyone's idea of an ideal size.  High end CRTs generally came in sizes up to 36" and sometimes even 40".  People with fond memories of large screen classic gaming will need to look for something larger.

In addition to the utter failure of the Zapper or R.O.B. or anything else that relies on the specific optical properties of a CRT screen working with an LCD screen, RF and composite video game signals look terrible on LCD screens.  Even a Framemeister cannot really do much here, the source of the signal is just too compromised.  The NES's signal is especially unsuited to the perfect digital flat-screens of today.  It's video signal is a bit gritty and what should be straight vertical lines come across as rather ragged with a three-line stairstep pattern. The lack of razor-sharp definition in a CRT can hide some of these flaws and turn others into an asset (dithering).

The final good thing about the Sylvania and TVs like it is that the can often be acquired for cheap to nothing.  People are only too happy to give these TVs away.  Thrift stores generally sell them for $5 or less.  You can find them if you are willing to dumpster dive or take TVs left on the side of the street.  I know of no other way you can get great image quality with full compatibility for classic video game systems so cheaply.

The Purity of RF Output

Before the NES and Sega Master System, all video game consoles only supported RF output.  RF combines video and audio output and modulates those signals into frequencies suitable for an analog TV.

Analog Television Broadcasting

Until the mid 1980s, there were typically only one type of input on an US TV, RF terminals.  There were a pair of screw terminals to attach the cable for a VHF antenna and a pair of screw terminals to attach a UHF antenna.  The VHF antenna mounted on top of the TV and comprised of two telescopic metal rods that could bemoved, a.k.a. "rabbit ears".  People would have to adjust these rods to get the best signal for each channel or invest in an externally mounted antenna.  A typical UHF antenna was just a big, round loop that was not really capable of adjustment.  VHF used channels 2-13 and UHF 14-83.  Typical TVs would have one dial for each.

With Digital Television, the same VHF and UHF channels are used, but the ATSC signals are digitally modulated and are vastly different from the analog NTSC signals.  In the advent of digital TV, analog TVs cannot understand the encoding of the digital signal and these dials are useless as of September 1, 2015 without a digital converter box.

RF Switchboxes

A typical pre-crash (1st and 2nd generation) console came with an RF switchbox with a pair of prongs that screwed into the VHF terminals with the wire for the VHF antenna.  The VHF antenna would have a wire with two prongs on it which would screw into a pair of terminals on the switchbox.  The old-style switchboxes would have a sliding switch with the label TV/GAME.  When the switch was slid to the TV, the TV would receive regular broadcast reception.  When set to GAME mode, the switchbox would block the over the air signals and let the console's signal go through.

The 4-port Atari 5200 and the RCA Studio II use unique RF Switchboxes which also provide power to the console.  Other US consoles use generic switchboxes.

RF Modulators and Channel Select

All home console systems of the first and second generation of video games connected via this method.  Inside each console is an RF modulator that takes video and audio information and modulates them into a signal a TV would recognize as sufficiently similar to a broadcast signal that it would demodulate it into picture (hue, saturation and brightness/luminescence and sync) and sound.  The original Fairchild Channel F used and internal speaker like many of the Pong home consoles, and the RCA Studio II does not output color.  The difference between the TV station and a console was that the TV station typically broadcast over the air and the console sent its information directly through a wire.

Consoles in the US "broadcast" on channels 2 (54-60MHz), 3 (60-66MHz) or 4 (66-72MHz).  Early consoles may not have had a channel selector switch.  The Fairchild Channel F and some heavy-sixer Atari 2600s do not have a channel selector switch and broadcast only on channel 3.  Channel 3 was not typically used by TV stations.  Channel 2 was usually the local PBS station and Channel 4 often belonged to one of the big three network's local affiliate.  Other heavy-sixers and all later Atari 2600s have a channel selector switch, channel 2 or 3 can be selected.  The RCA Studio II, Atari 5200 and 7800 also use channel 2 and 3.  The Arcadia, Odyssey 2, Astrocade, Intellivision and Colecovision allows channel 3 or 4 to be selected.  This would become standard in post-crash systems.

RF Connectors

Even in the early 1980s, some TVs were coming with a screw-threaded coaxial connector instead of the two screws for VHF.  In this case, early TV switchboxes would require a 300 Ohm to 75 Ohm connector.  Later switchboxes, like for the NES, SMS and every console thereafter, would only use coaxial wires.  To connect to an older TV, reverse connector, the 75 Ohm to 300 Ohm connector, would have to be screwed into the VHF screw terminals of an older set.  Even Atari eventually released a coaxial version of its manual switchbox.

Today, unless you rely on OTA transmissions, typically the only thing a TV coax screw will be used for is cable input.  Newer high definition capable cable boxes use HDMI and Component video for the Hi-Def signals. If you are not using this coax for cable, you can typically connect a simple RCA to coax adapter and toss the switchbox.  Some switchboxes, like the ones you could buy from Radio Shack, degrade the signal.  Other switchboxes, like the most recent Atari switchboxes with coaxial wires, do not, so I have read.

Exceptions to the General Rule of RF Availability

No pre-crash console allowed for composite video output.  Mods were not generally known during the pre-crash era or for many years thereafter.  Composite video monitors were seldom found outside of studios and computer monitors until the mid-1980s when VHS players became ubiquitous in US households.  However, composite video and audio may be appropriate for two systems, the Atari 5200 and Colecovision, due to their computer based roots.  The Atari 5200 uses the same chips and behaves similarly to the Atari 400 and 800 computers.  The Atari 800 had a jack that provided composite and separated chroma/luma output. Composite video was found on computer monitors at this time.  Separated chroma/luma is essentially S-Video.  I would strongly advise against an S-video mod because it eliminates the composite artifacting effect that games like Choplifter on the 5200 use.

The Colecovision uses the TMS9928A Video Display Processor, which natively outputs a form of component video which is converted to RF in the system.  The Colecovision only offers RF, but the Coleco Adam, which can play Colecovision carts, offers composite video and audio.  Coleco composite, S-video and even component video mods exist.  Also, the Colecovision is a very close hardware cousin to the MSX home computers, which could support RGB video.  Many MSX games have been ported to the Coleco in recent years.

3rd Generation & Beyond

The NES and SMS switchboxes did not have a sliding switch. Instead, the signal from the console would switch the signals automatically when the console was turned on.  Earlier consoles do not provide the power to cause the switch automatically.  Both also allowed for composite video and audio connections and came with AV cables.  All post-crash systems could provide at least composite video (in their first iteration at least and some require special cables or an adapter).  For this article, the Atari 7800 is a pre-crash system, it was designed and test marketed before the crash.

Of course, I must make an exception to the exception for the Japanese Famicom, released in 1983 and which would become the NES when released in the US in late 1985.  By its date, the Famicom is in the 2nd Generation, but its graphics and sound capabilities are substantially superior to any second generation console.  I recommend that the Famicom be modded to support composite video like the NES, the Famicom AV, the Twin Famicom and the Sharp Famicom and NES TVs.  However, the best mods may require lifting the PPU out of its socket and placing a copper sheath around it, so that is not for everybody.

The Famicom only supports RF output, but the Japanese TV broadcasting used different frequencies than US broadcasting.  The Famicom broadcasts on Japanese channel 1 (90-96MHz) or 2 (96-102Mhz).  In the United States, these broadcast frequencies were and are assigned to FM radio (87.9-107.9MHz).  Japan's FM radio frequencies (76MHz-90MHz) are mainly taken up in the US by TV channels 5 (76MHz-82MHz) and 6 (82MHz-88MHz).

On higher end CRTs sold in the US, channels 95 and 96 tune to the Japanese channel 1 and 2 frequencies, respectively.  No TV manufacturer ever intended that these channels would be used to receive over the air broadcasts.  These channels were a late addition to the US channel lineup and placed in higher end TVs that were intended to be marked in NTSC countries like the US and Japan with only minor changes to the TV's firmware necessary to assign the appropriate channels to the appropriate countries.

The Famicom came with a white RF adapter with some screw terminals.  A (S)NES or Sega Master System/Genesis RF adapter can be used, but you will need to use the switches on the back of the Famicom to switch the input and the channel.

Home Computers

When the Apple II was first released, it had an RCA composite video output jack and a video pin header on its motherboard.  However, most buyers of the device only had a TV set with antenna leads.  Third parties marketed RF modulators that plugged into the header on the motherboard and connected to an external RF switch.  The most popular one was the Sup'R"Mod. II, which came out in a version that broadcast on Channel 3 and another version that broadcast on Channel 33.  This is the only example of a popularly available RF modulator broadcasting on a UHF channel.

When IBM released the PCjr., it believed that many buyers would want to hook it up to a standard TV set.  It designed and released an RF adapter with a special 2x3 BERG connector that was keyed for the Television port on the back of the PCjr.  This adapter took a standard video and audio signal from the PCjr.  The adapter was in a long, silver box and contained both the modulation circuitry and the switchbox circuitry.  It had a "TV/Computer" switch and a Channel Select (3-4) switch.  Unfortunately it only has screw terminal input and output, so you will need both types of converters to use the box on a modern TV and with cable TV input.  This photo shows a fully modernized version of this beast :

IBM had previously released the IBM Color/Graphics Adapter.  This adapter had an RGB monitor output, a composite video RCA jack and a header for an RF adapter.  IBM never released its own RF adapter for the PC.  The RF is 4 pins and is identical to the Apple II header except it does not have the pin or connection for the -5v line.

Matching Transformers

Twin lead connectors require 300 ohm impedance connections.  Coaxial connectors require 75 impedance connectors.  Therefore, in addition to using completely different physical connectors, electrically these signals are not quite compatible.  If you are trying to use one type of connector with another type of connector, you need an appropriate matching transformer, or Balun.  A 300-to-75 ohm transformer, shown in the top of the above photograph, will allow you to connect to a coaxial connector on a new TV.  A 75-to-300 ohm transformer, shown on the left of the above photo, will allow you to connect a twin lead connector on an old TV.  These can be purchased cheaply at Radio Shack.

Conclusion

Prior to the 3rd generation, home video game consoles were often treated as toys and marketed and designed as such.  High end video connections had barely reached into the home.  Higher end-audio was somewhat more common, but there is not a lot of sophisticated music to be heard in the pre-crash era.  The B&W switch on the Atari 2600s was not placed there simply for cosmetic purposes, many game consoles connected to B&W TVs.  Consumers were generally satisfied when they got the system to work.  RF provided a known quantity for programmers, they had to make their graphics look clear with it.  Tiny text and high resolutions lost much of the detail on the modulated signal.  RF was the way these consoles were meant to be seen.  Except where indicated, it is the way these consoles should be played.  Anything better is not true to the classic console experience.

Youtube No Longer Sucks for Retrogaming Videos

Last year, I made this blog post, http://nerdlypleasures.blogspot.com/2013/10/youtube-sucks-for-retrogaming-videos.html, when I complained that Youtube will cut the frame rate of your video in half.  Anything recorded in 60 frames per second will be converted and shown at 30 frames per second.  This can have an awful effect on the resulting video.  Flicker, a frequent issue in retro consoles, will make sprites disappear when, with the full frame rate and proper persistence of vision, they would not completely disappear.

As of October 29, 2014 (a year and a day from my original post, now coincidence there), Youtube now supports 60fps with 720p and 1080p resolution video.  Strangely, it does not support it in lower resolutions, 144p, 240p, 360p and 480p.  However, by upconverting lower resolution videos into higher resolution, we can preserve the resolution of the video and the frame rate.  Take, for example, this sample video I created :

https://www.youtube.com/watch?v=I16xSHMKaLc&feature=youtu.be

The maximum resolution is 720p60(fps).  For once Youtube is not hiding the frame rate anymore.  So how did I get this?

First, I recorded gameplay footage using an emulator that can record to AVI and that supports DOSBox's ZMBV Codec.  This Codec is very friendly to 8-bit graphics, and can provide lossless video compression.  For NES emulators, Nestopia Undead Edition, when the Movie Capture function works, it works perfectly.  Record the movie, export it to AVI and select the DOSBox ZMBV Codec.

Now you should have an AVI video, but the resolution is 250x240@60fps.  We need to convert it to something that Youtube will allow to be viewed at 60fps.  Fortunately, 240 x 3 = 720, which is the vertical resolution of 720p.  256 x 3 = 768, so we will need to add borders to our video to get to the full 1280x720 resolution Youtube demands of the video.  VirtuaDub is a good program to accomplish all this.  The last version of VirtuaDub is 1.10.4, and it only works with AVI files.  Load your AVI file, go to the Video drop down menu, then Filters, and select resize.  On the options dialogue for filters, use New size Relative 300%, Aspect ratio Same as source and under Framing options, Letterbox/crop to size 1280x720.  (If you want 1080p, use Relative 400% and Letterbox to 1920x1080.  I am not sure whether 1200p is supported in Youtube at 60fps)  I would suggest using nearest neighbor as the Filter mode, you should keep your video sharp, Youtube will compress it losslessly.

Next, under the Video drop down menu, there is an option for Color Depth.  You should select 16 bit RGB (5,5,5) or 32 bit RGB (8,8,8 dummy alpha channel), depending on the amount of color your video has.  For NES and SNES games and systems of similar vintage, 16-bit RGB is fine.  Then,  under the Video drop down menu, click on the Compression option.  Select Zipped Motion Block Video 0.1 (that is what ZMBV stands for).  This is the DOSBox compression codec, and it will produce great results.

Finally, go to the File drop down menu, click on Save to AVI.  Type in the name of the resulting AVI file and watch VirtuaDub do its thing.  When the Progress bar is totally green, you will have your HD file.  All you need to do is to upload it to Youtube and tell people to watch it in HD.  Of course, if you want to edit it, add audio commentary or whatever, feel free to do so, but this method will allow you to display 60fps video of retro consoles without difficulty.  It also works with most computer emulators such as DOSBox.  The CGA, EGA, Tandy and PCjr. machine types output 60fps using DOSBox's movie capture function.  The vgaonly and SVGA, on the other hand, outputs to 70fps in most modes, which Youtube does not support.  You should use one of the earlier machine types for any non-VGA mode so you only really need to worry about games using the 320x200x256, 640x480x2 and Mode X modes.  VGA 640x480 runs at 60fps as may SVGA modes unless they allow you to set the refresh rate.

Those videos with output by DOSBox in 70fps will have to be converted to 60fps, which will not affect most games because they only put out as many frames of animation as they need.  For games using any 320x200 modes, you should resize it to 1600x1200 to obtain the correct 4:3 aspect ratio.  Even though a VGA upload will not be perfect, the results are still very good, as you can see here :

https://www.youtube.com/watch?v=jE_IZNHUu08&feature=youtu.be

Additionally, the Hercules machine type and all PAL console emulators output 50fps.  Fortunately, Youtube supports 50fps as well as 60fps, as you can see here :

https://www.youtube.com/watch?v=uH8RPoEo_Mc&feature=youtu.be

While Youtube may not be the perfect video uploading service for retrogaming videos, with support for 50fps and 60fps, although requiring HD, it has come a long way to remedy one of the worst video quality problems for retrogame footage.  While I believe Dailymotion may also support high frame rate videos, few other video sharing sites do, and Youtube is the one that earns the most traffic.  I would hope that the site would eventually add support for low resolution videos (which would allow for smaller files and save bandwidth), but today with simple conversion tools, viewers need no longer suffer from jerky motion, unnatural movement and disappearing sprites.

Oddball EGA and VGA Resolutions, When the Standard Resolutions Aren't Used

I have already indicated in several posts that 320x200 was generally the resolution for DOS games.  However, in my previous post I discussed how the classic DOS pinball games use Mode X resolutions.  In this post I will identify other games that use non-standard resolutions.  While there are a few games that use oddball EGA resolutions, custom resolutions really came into play with VGA.  Once people figured out how to manipulate its CRT Controller Registers without destroying their monitors, all manner of resolutions became possible.

In addition to supporting all CGA Graphics and Text Modes and the MDA Text Mode, the standard BIOS Supported EGA graphics modes are :

Mode 0Dh - 320x200x16
Mode 0Eh - 640x200x16
Mode 0Fh - 640x350 mono (intended for monochrome MDA monitors)
Mode 10h - 640x350x16/64 (can display 16 colors from palette of 64 colors, requires color 350-line monitor)

In addition to supporting all the mode EGA supports, the standard, BIOS Supported VGA graphics modes are :

Mode 11h - 640x480x2 (intended for monochrome analog VGA displays, MCGA compatible)
Mode 12h - 640x480x16 (60Hz, all other VGA modes run at 70Hz)
Mode 13h - 320x200x256 (MCGA compatible)

For the list of games, I have taken my own screenshots with DOSBox.  Any aspect ratio correction from DOSBox has been removed.  If no scalers or aspect ration correction settings in DOSBox are used, 320x200, 320x240, 360x200 and 360x240 resolutions are not scaled.  Other resolutions are stretched as follows :

320x350 to 640x350
320x400 to 640x400
320x480 to 640x480
360x350 to 720x350
360x400 to 720x400
360x480 to 720x480

Certain resolutions, like 320x240, need no aspect ratio correction, since that mode was used to ensure square pixels.  Many of these modes may not fill to the edges of a VGA monitor.

Gauntlet

256x200 EGA Mode :

Gauntlet uses this mode, which seems derived from the 320x200 16-color mode.  Gauntlet and F-15 Strike Eagle also use an unusual for EGA 160x200 16-color resolution, but this may not be an actual new mode as just drawing every pixel twice in the 320x200 16-color mode.  Sierra's AGI games also use an effective 160x200 graphics resolution, but use the typical text font for the 40 column text modes, which require 320 horizontak pixels.

Lemmings & Oh No! More Lemmings

These games change the palette entries in mid-frame in order to select more colors than would be normally possible in the 640x350 16-color mode.  Lemmings uses this only for the screen type below, and no other place.  Regular DOSBox v0.74 will show these proper screens with the vgaonly machine type.

640x350x"32" EGA Mode :

640x350x"32" VGA Mode :

Pinball Fantasies

Same issue with Pinball Fantasies, but only on the table select screens and using a different resolution. Without this effect, the car would look mostly green.

640x480x"32" :

Pinball Illusions

Pinball Illusions is one of the most demo-like games ever released by a developer with any stature in the PC DOS game world of the time.  It uses several weird modes and very demo-like effects.

320x400 :

These graphics should obviously be stretched horizontally.

320x145 :

320x290 :

These banners should also be stretched horizontally to fill the screens, they look wrong without aspect ratio correction.

320x240 (304x224 active pixels) :

This screen is very interesting.  The active screen is 304x224 pixels, and this is what DOSBox captures in a screenshot.  On a real monitor, there is this dark blue border seen in the screenshot.  You can see this border in a custom version of DOSBox like daum that has border support.  I had to add the border in this screenshot, and I figured that 8 pixels on each side would ensure that the screen ratio was 4:3, those are rotating cubes.

Jurassic Park

This game is clearly an Amiga port.  One of the main game types uses an odd 320x184 mode.  I suspect that it was done for performance issues, as the same resolution is used for the Amiga.  The game uses 320x200 for the other game type, which is a first person 3D shooter.  However, the Amiga confines the action to a small window, whereas the DOS version the action takes up most of the screen.  Some Amiga screens use a 320x256 resolution (found on PAL Amigas), including the loading screen.  The loading screen shows a perfect circle, whereas the same screen in the DOS version, which uses 320x200 pixels, does not without aspect ratio correction.

320x184 :

Prehistorik 2

Why did the programmers decide to eliminate 8 pixels from the standard resolution?  Because they could, evidently.  Game uses 320x200 elsewhere, including on the in-game screen.  The difficulty selection screen shown below uses a typical demo effect.

312x200 :

Cyril Cyberpunk, a.k.a. Cyberboard Kid

288x224

No aspect ratio correction required.

Jazz Jackrabbit & Jazz Jackrabbit : Holiday Hare '94 & '95

320x199 :

I hypothesized earlier that the programmers made a tiny tweak to the standard mode to ensure that the adapter would run this mode at 60Hz, not the default 70Hz. The question of whether the game requires aspect ratio correction is complex.  The in-game screens clearly do not :

If you look at the circles in the last two screenshots, you can see that they are perfectly circular.  Aspect ratio correction would only stretch them into ovals.  Similarly, the large and small "diamonds" in the first two screenshots are actually squares, as each of the four sides has the same length.  In fact, on a real VGA CRT, the in-game graphics should appear in a letterbox mode with large borders on the top and bottom.  However, if the user decides to stretch out of screen vertically, then the objects will become elongated.  There are no other near modes that would show the detrimental effects of the stretch, so the effect may be lost.  

On the other screens, some may require aspect ratio correction, while others do not.  Here is one that does not :

On the other hand, this one does :

The planet in the middle of the screen doesn't look quite right without aspect ratio correction.  Even with aspect ratio correction, its not a perfect sphere, but neither is the real Earth :

The Incredible Machine & The Even More Incredible Machine

Sierra bought several companies in the early to mid-1990s, and while their own games rarely pushed hardware, the same cannot be said for some of its subsidiaries, like the one that produced this series of games.  These games do not require aspect ratio correction.

640x471x16 :

640x400x16 :

640x448x16 :

The Incredible Machine 2

640x441x16 :

Quake

Quake is unique because it supports every combination of 320 and 360 horizontal pixels and 200, 240, 350, 400 and 480 vertical pixels.  Increasing the vertical resolution increases the view area vertically.  This looks absolutely ludicrous without aspect ratio correction once you get to 350 vertical pixels.  Increasing the horizontal resolution puts empty filler on the sides of the status area and does not enhance the field of view horizontally.  Instead, it merely stretches the pixels contained within that view horizontally.  I would personally recommend staying with the 320x240 resolution.  At 640x480 resolutions, you should really be using GLQuake (with a Glide wrapper if necessary) or a source port with support for more modern 3D accelerators.

320x240 :

320x350 :

320x400 :

320x480 :

360x200 :

360x240 :

360x350 :

360x400 :

360x480 :

Earthworm Jim & Earthworm Jim 2

Earthworm Jim was originally designed for the Sega Genesis, which uses a 320x224 pixel resolution.   320x240 is used for all non-ingame screens in both EWJ1 and EWJ2.  Both 320x224 and 320x240 are available for EWJ1 in-game, but EWJ2 supports only 320x224.  There is no difference between the two graphics modes in EWJ1 except the need to adjust the size graphics using the monitor controls, but some cards had trouble with the 320x224 mode.  Due to the origins of this game, it should be stretched out vertically, but tiny difference between 224 and 240 pixels makes it pretty much a non-issue.

320x240 :

320x224 :

The Lost Vikings & Norse by Norse West: The Return of the Lost Vikings

320x240 :

LineWars II

This is the only Mode X VGA mode the game supports, and it requires horizontal stretching.  This game will support 640x480 and 800x600 on specific ATi and S3 SVGA cards.  The regular 320x200 resolution does not need aspect correction, but the 320x480 resolution obviously does :

320x200 :

320x480 :

Scorched Earth

For the main menu, each increase in the graphics resolution adds more height to the image.  As a consequence, the buttons are more spaced out vertically.  However, as you can see, the 320x240 resolution cannot fully display all the buttons using the spacing, which is consistent beginning with this resolution.

320x200 :

320x240 :

320x400 :

320x480 :

360x480 :

As far as the in-game graphics go, each increase in resolution substantially increases the play area, but not the status bar.  As you can see, the amount of barrier to open space ratio eventually becomes ridiculous :

320x200 :

320x240 :

320x400 :

320x480 :

360x480 :

Aspect Ratio correction required.

Chaos Software Mario Shareware Game

320x190-191 :

The top eight pixels do not seem to be used, but sometimes an extra black line is displayed, leading to the one pixel difference.

Axia

640x400x16 :

Needs no aspect ratio correction, the planets are perfectly spherical without it.

Jump 'n Bump

400x256 :

Most Moraff games

Games shown are Moraff's Flygame, Moraff's Super Entrap and Moraff's Monster Memory

360x480 :

Monster Memory's unadjusted 360x480 resolution is clearly wrong compared to its true 4:3 SVGA modes, which show perfect squares.  In addition, the 320x200 mode does not show perfect squares unless aspect ratio correction is applied.  I would think this applies to all of Steve Moraff's games, since they were developed by him.

I am greatly indebted to RGB Classic Games for identifying many of the more obscure games on this list. Moraff's (Regular) Entrap and Magic Pockets do not use a 640x400 VGA mode, despite what RGB Classic Games may think.  Moraff's Entrap, as it states in its setup menu supports EGA 320x200, EGA 640x350, VGA 320x200 and VGA 640x480.  Magic Pockets supports regular EGA 320x200 (but uses different palette entries than the Tandy 320x200 mode) and regular VGA 320x200.

The Moraff games that support the 360x480 mode are as follows :

Moraff's Blast I
Moraff's Dungeons of the Unforgiven, Module I
Moraff's Monster Bridge
Moraff's Monster Memory
Moraff's Super Blast
Moraff's Super Entrap
Moraff's Mega Morejongg
Moraff's Stones
Moraff's World

Moraff's Escapade only supports OEM-specific SVGA modes found on Ahead Systems, Trident and Tseng Labs chipsets with 1MB of RAM.

System Shock CD

Unlike the floppy version, which supports only 320x200, the CD version also supports 320x400, 640x400 and 640x480.  While the 320x400 resolution clearly requires aspect ratio conversion, the 320x200 and 640x400 modes do not.  They have perfect squares and circles in the HUD area, and the 640x480 mode distorts them into rectangles and ovals.

320x200 :

320x400 :

Conclusion

I believe there are to types of non-standard VGA modes, first there are the the modes that use a combination 320 or 360 horizontal pixels and 200, 350, 400 or 480 vertical pixels.  Second, there are modes that use a number of pixels other than the ones given in the previous sentence for at least one axis.  The second variety are the games that tend to break graphics cards with less than stellar VGA compatibility.  Even the first variety can cause later cards to break because there was no universal standard.  

As far as aspect ratio correction with non-standard VGA modes go, it is almost always desirable to stretch out the double the horizontal pixels for any of these games that use a 320 or 360 horizontal pixel resolution.  Often, there will be a standard VGA or SVGA mode to guide you.  I understand that VGA cards more or less do this by default in low resolution modes.  However, this does not always apply, as I have demonstrated in the previous post with the 360x350 mode used by Pinball Dreams and its successors.  

With games that use a high resolution 16 color mode with 640 horizontal pixels, I see no reason to stretch the display vertically.  The letterboxing is pretty minimal.