Friday, August 5, 2016

The Generic DOS PC - A Critique of LGR's 486 Build

If you wanted to build a DOS PC, what would you build?  The answer depends in no small part on what you expect it to run.  Do you want a system that can run the oldest games?  In that case you will probably want an IBM PC, XT or one of the earlier Tandy 1000 series systems.  Perhaps even a PCjr. or a Compaq Portable?  But those systems are often running PC Booters as much as they are running true DOS games.  Fast forward a couple of years and you get into EGA and VGA systems.  Now you are dealing with higher speed 286s, 386s and 486s.  Even though many of the more speed sensitive games will fail to run on these systems, the classic DOS era is at hand.  But suppose you want something with 3-D acceleration and high resolution color in mind.  Then you are looking at Pentium systems and sharing drive space with Windows 95 games.  Duke Nukem 3D, Fallout, Magic Carpet 2 require more than what most 486s will give.

I would suggest that most people probably received their first introduction to IBM compatible PCs and DOS in the early 1990s, "When VGA Was King."  In those days, then-young adults like myself were in awe at the beautiful graphics of the King's Quest games, addicting world-building simulations like Civilization and complex role-playing of the Ultimas.  We saved our allowances to buy a Sound Blaster card because systems did not come with sound cards as a standard feature until well into the mid-90s.  We looked eagerly at the new CD-ROM technology, waiting for it to drop in price and salivated at The 7th Guest and Myst (and found out that cutting edge technology seldom lives up to the hype).  PCs had something to offer that our NES, SNES and Genesis consoles could not.

Building a DOS system often addresses that era of early 90s gaming with the ability to reach somewhat back to the late 80s and forward into the mid 90s.  Building vintage computer systems has become something of a niche hobby, but now one with very dedicated members.  My own humble writings here and elsewhere may have made some small contribution to this phenomenon.  But when someone like Lazy Game Reviews decides to post a system build video, it will get a great deal of attention.  With almost 400K Youtube subscribers and videos easily ratcheting 100K views within a short period of time, he is sufficiently successful on that he does not need a day job.  Although far many more people watch his Sims videos than his retro-computing videos, there is enough overlap that his message reaches many more people than anyone else I know of who regularly covers retro-PC topics.

Here is his first video :
And here is his followup video :

You should watch or at least peruse these videos, they are full of detail and entertaining.  I do not intend to nit-pick at everything in these videos.  Instead I will point out what I found to be good and what I would have done differently.

His system, as revised by his later video, is a good one for people looking for a first-time system build to get started with.  The CPU is a 486DX2/66, an excellent balance between speed and versatility.  These CPUs work in 5V motherboards, later CPUs require 3.3V or 3.45V capable boards.   They are easy to find and with a heatsink/fan, run very reliably and not too hot.

Even though a 486DX2/80 and faster processors may fit inside a Socket 3 motherboard, without a proper voltage regulator that CPU is toast.  Remember that 8-16MB should be all that system needs, no more, no less.  The motherboard should have at least 1 VLB slot and hopefully you can find one with a coin-cell battery holder and not the barrel batteries or even worse the RTC module.  Otherwise you will need to breakout your soldering and desoldering equipment.

A 486DX2/66 system is best used as a pure DOS system although it will also run Windows 3.1 very well.  Finding a reason to run 3.1, that is a story for another blog entry.  For graphics, a VLB card should be used if you can find one.  I like VLB cards using the Cirrus Logic GD5428 chip, a fast and compatible chip.  Coincidentally, so does LGR. They are much faster than ISA video cards and can be had at reasonable prices.  Most can be upgraded to 2MB of DRAM, but the upgrade is not a must.

For his system build, he started with an AWE32, but I believe that was overkill for this system.  An AWE32 has its place with Windows 95/Pentium systems, where it is better suited.  If your video card BIOS is a little early, UniVBE can help fix problems with SVGA games (640x400x256 colors is a popular mode that was adopted a bit late by some vendors).  For similar reasons, I shy away from PCI 486 motherboards, those are for advanced builders with money to spend.

His eventual choice of a Sound Blaster Pro 2.0 is probably the best single-card solution you could have.  The Pro 2.0 will give you FM music and sound effects (or digital sound effects) with almost any game and does not really need much in the way of a driver installation.  I simply recommend installing the driver package to get the pre-output volume from the mixer to a decent level and to turn off the low-pass filter.  With SoftMPU it can work with quite a few of the Intelligent Mode MPU-401 games.  A Sound Blaster 16 will work almost as well and they are often cheaper.  A Sound Blaster 2.0 is almost as good and also reasonably priced.  When you no longer feel satisfied with FM Synthesis, then you should consider upgrading to a MT-32 or Sound Canvas.

As far as storage goes, use what works.  I would suggest a 3.5" HD floppy drive, but a 5.25" HD floppy drive would also work and may be necessary to save backup your old game floppies.  You can use both, I use a combo unit with both types of drives in my 486 that takes up one bay.  That Gotek floppy emulator is good enough to install DOS and probably works OK with standard disk images.

Unlike LGR, I have never had a problem using Compact Flash and DOS that I could trace to the CF card.  CF cards are really fast and DOS does not write to the hard drive often.  With a CF card, installed in a user-accessible bay, I do not really find a network card to be necessary.  When it comes to a CD-ROM drive, you are definitely better off for getting something that works (even a DVD drive) over something that is period correct.  Hard drives and CD-ROM drives have working parts, gears, motors, and the like.  Time is not kind to them, as demonstrated by the colossal disappointment of a new-in-box drive LGR tried to install in the first video.

Since this is a custom built pre-PCI 486 system, you will not find any connectors on the motherboard.  You will need an I/O card, and most should come with ports for 2 serial, 1 parallel, 1 floppy and 1 hard drive.  Some come with game ports, but they are redundant with a sound card.  You should stick to IDE hard drives and ISA I/O cards.  While VLB IDE may speed up drive access, it is not necessarily the most stable way to connect a hard drive, and having to reformat and copy your games back over to your CF card is a pain in the butt.  More devices on the VLB tend to cause issues, so give your graphics card priority here.  Of the serial and parallel ports, only one serial port is really necessary, and that is used for a serial mouse.

The last issue is external cache.  LGR's system did not put any in his motherboard.  Many motherboards come with 256KB of cache, more than that in a system of this speed is really bucking up against the law of diminishing returns.  Many OEM systems omit the cache as a cost saving measure, but often support I/O (including PS/2 mice) on their motherboards.  I am not persuaded that external cache is going to make an unplayable game playable.  It might help somewhat in some of the more monster-stuffed levels in DOOM II, but don't expect miracles.  Replacement cache chips are easier to find on a motherboard than as individual memory chips.

Ultimately, LGR's build is a solid build for someone looking to enjoy DOS games on real hardware.  My 486 is very similar to it, even if I eschew woodgrain :)  The choices are solid for someone who would like to have a retro PC and expect that most of their games will work with good graphics, sound and music.  Nothing in the system is incredibly expensive.  When you are looking to build a system, it is important to do research and his videos and his channel are well-recommended as an importance source of information for this hobby.


  1. He installed L2 cache to the 486 in his newest video. Not bad, made Duke 3D almost playable...

  2. You should make a Review of the Dos-Part of the performa630Dos :)

  3. I, along with a few other people, have a bigger problem with LGR's machine: there's something deeply broken with it, maybe in the BIOS settings, maybe in the memory used or how it's been installed. The memory speed is EPICALLY slow for a 486, it's more in the range of a fast 286, and it's what lies behind the machine's utterly hopeless performance in Duke3D and the like (even moreso than the ISA video card, which at 320x200 shouldn't be a significant bottleneck). The lack of cache really doesn't help in this case, but the thing is, if your machine is set up properly and has quick memory in the first place, it should make minimal to no improvement for most 486 gaming usage cases. As demonstrated with my own 486 SX/25, where the measurable speed difference between RAM, L2 and even L1 cache (the latter would of course be faster with a DX2) is no better than about 5%... and in all cases considerably faster than what LGR measured for his machine's memory speed (despite it having a 33% faster bus and 166% faster CPU, and what should be, at worst, the same memory tech as my entirely random 30-pin SIMMs).

    Just goes to show that even with classic hardware it's possible to make an absolute balls of the setup. The performance he demoed is more like what you'd expect from an even slower 486SX, maybe an SLC, or more likely a medium speed 386, and nothing like what I remember getting from our own DX2 with the same games.

    FWIW, I would contest the avoidance of PCI in favour of VLB unless you're aiming for that very specific, short period where ISA was becoming a bottleneck and PCI was yet to arrive/establish itself as a rival to MCA and EISA, so people were putting up with the absolute crawling horrorshow that was VESA local bus. PC mags of the time recommended ditching it like a hot rock as soon as there was any kind of alternative, and their letters, troubleshooting and advice pages frequently featured the problems people were having simply getting their VLB systems to reliably boot. We bought our first PC in mid 1994. It was a midrange multimedia model, with an AMD 486 DX2/66, 8MB in 60ns FPM 72-pin SIMMs, a 540MB Seagate IDE HDD running initially PIO Mode 4 but later 16.7MB/s DMA mode 2 when a reliable Windows driver was avaiable, some kind of cache (128KB?), an ESS audiodrive ISA audio card, generic 2x CDROM drive, relatively capable 15" CRT... and a 2MB Avance Logic PCI video accelerator, obviously on a PCI motherboard (the HDD controller and some other northbridge stuff was also technically connected via that bus), with no sign of VLB anywhere. In fact, I have yet to run across a VLB machine in the flesh, but I've run across enough ISA 286s thru 486s, and PCI 486s and Pentiums... So unless the comment is about the actual price of boards on eBay rocketing, it wasn't actually that high-falutin' or unusual a thing at the time, and was in fact the recommended way as soon as it became practical.