Sunday, April 26, 2015

Turbo Duo - Issues and Solutions

The Japanese PC Engine console was released as the TurboGrafx-16 in the US in 1989.  Conceived as a competitor to the NES and the Sega Genesis, it flourished in Japan, floundered in the US and barely had a presence in Europe.  However, it has many great arcade ports, fun platformers and lots of Shoot-em-ups.

Using HuCards

The TurboGrafx-16 can be a very expensive system to collect games for.  Japanese systems use HuCards for the games on ROM.  HuCards are slightly thicker than a credit card and have exposed contacts which get inserted into the card slot on a Turbo system.  Some US material called them TurboChips.  Japanese and US HuCard games are functionally identical but not pin compatible, requiring a region mod or a converter PCB to use cards for the other system.

However, it  is surprisingly easy to play games on any NEC system these days if you don't want to engage in the pricey journey to collect HuCards.  A Turbo Everdrive from Krikzz will play any official, licensed game (with one exception, see below). The Everdrive has a switch to select the console's region and an SD slot to load ROMs. The current card is flash based and loading a new game requires rewriting the old game.  The currently written game can be selected instantly by pressing the select button.  Writing a large 1MB game like Bonk's Big Adventure only takes about 11 seconds. There will be a newer, RAM based version released in the near future that will make loading faster and end worries about reaching the write limit of the flash media. However, the media should be rated for at least 10,000 write cycles, so if you flashed a new game every day it would take you at least 27 years to exhaust the memory.

The Everdrive can also be used as a CD System Card 2.0 replacement by loading the ROM.  It does not have the extra RAM needed for Super CD System 3.0 Card support or an Arcade Card.  It will work with the game Populous only in the Turbo/PC Engine Duo console line because that game came with extra RAM that is duplicated in the CD systems.  However, you can include the Super CD System ROMs so you can play CD games with an Everdrive installed in your Turbo Duo.  You can also load the US ROM in case you forget what the save RAM options are if you have a Japanese system.

One other irksome issue with regions is that the PC Engine uses a different gamepad connector from the TurboGrafx-16.  All Japanese consoles uses a mini-DIN-8 connector while TurboGrafx 16s use a DIN-8 connector. The US Turbo Duo also uses the min-DIN connector.  The controllers and multitaps themselves are otherwise compatible and there are converters available.  Japanese controllers and multitaps are often easier to find than their US equivalents.

A final issue is that the original PC Engine and TurboGrafx-16 were RF only.  The TurboGrafx-16 required a Turbo Booster or the TurboGrafx CD add-on for stereo composite AV output .  The PC Engine usually did the same through the PC Engine CD.  As I mentioned in my RF blog entry, Japanese RF channels are not the same as US RF channels.  NEC later released the Core Grafx and Core Grafx II consoles which replaced RF with stereo AV output.  There is also the PC Engine Shuttle which supports stereo AV but has no expansion port for a CD add-on.

Using CD Backups

The TurboGrafx CD was the first CD-based console add-on.  It came with the CD unit, a Docking station and a CD System Card (2.0).  All three pieces are required to make it work with the TurboGrafx-16, and it makes the system look like a large, black inverted-T.  The system could be upgraded to play Super CD-ROM games with a Super System Card (3.0).  These are hard to come by for the US console.

In 1992, the TurboGrafx-16 and TurboGrafx CD were released in a combined unit called the Turbo Duo. Japan's version is called the PC Engine Duo.  The Turbo Duo plays US HuCard games but uses the controller ports from the Japanese consoles.  It also uses a 5-pin DIN AV output connector which supplies composite video only and stereo audio.  Finally it has a stereo mini-jack for headphone output.  The Japanese version is identical except for the color of the buttons and the support for Japanese HuCards.

NEC later released the white PC Engine Duo-R which removed the headphone jack and the lock switch for the CD cover.  Finally, the PC Engine Duo-RX was slightly cosmetically different from the Duo-R but included a six-button gamepad.  Only a few Japanese games like Street Fighter II - Championship Edition supported the 6-button pad.

Any of the Duo consoles are expensive ($250-$350) to acquire, but playing backups of the CD-ROM games are cheap.  The original Duos will almost certainly need to have the capacitors replaced. The Duo R and RX have a reputation for being more reliable. The lens assembly may also need to be replaced.  However, you are really getting the full NEC console experience with one of these systems and it can play a ton of great games.

In burning CD backups, however, you have a challenge.  Turbo CD games rarely look like standard CD-ROMs.  Except for a very few CDs with only a data track, all CD games are mixed mode games with data and audio tracks.  For these games, the first track is always an audio track intended to warn the user not to play the CD in a CD player.  The second track is always a data track (and the reason for the warning), and for some of the simpler CDs, they only have one data track.  CDs with more complex mastering also have a second data track as the last track on the CD.

There is nothing inherently non-standard about mixed mode CDs.  Many, many MS-DOS CD games used a data track and one or more CD audio tracks.  Most Sega CD, Neo Geo CD, Jaguar CD, 3D0 and some Sega Saturn and Sony Playstation games used mixed mode CDs.  However, for the MS-DOS CDs, Sega CDs and Sony games, their CDs always have just one data track and it is always the first track.  One or more audio tracks follow.  Turbo CDs, even those with only a data track, are not readable in a PC except as an audio CD.

A good backup uses high quality media.  I have read good things about Taiyo Yuden CDs, and I have also used Sony SUPREMAS CD-Rs with some success.  Ideally these CDs should be burnt as slowly as your burner can burn them. However there are several caveats to this.  First, modern CD-Rs were designed to be burnt at 16x speeds or better, as are modern burners.  Second, if you use a really old burner it may not support the ideal settings for burning Turbo CDs.  The ideal setting is to use a CUE sheet (either with a BIN or ISO and WAV) in the Disk at Once mode.  Really old burners may not support Disk at Once or may balk at the nutty mixture of audio and data tracks some of these images have.

Compared to playing with original pressed discs, the CD motor may exhibit more noise and the load times may be longer.  Load times for pressed media are often very quick.  It takes virtually no time for even a 1x CD-ROM unit like the one in a Turbo console to switch and audio track.  Additionally, there is only so much RAM to fill in a Turbo system (8KB CPU RAM + 64KB Video RAM + 64KB ADPCM RAM + 64KB CD-ROM RAM + 192KB Super System Card RAM).  A 1x CD-ROM transfers at 150KB per second, so load times should be fairly reasonable.  When you get to Arcade Card games, which add another 2MB of RAM, things might take longer.

Here is a list of all US released CD games by their type :

Two Data Tracks US CD Games
Buster Bros.
Fighting Street
J. B. Harold Murder Club
Jack Nicklaus Turbo Golf
Last Alert

Two Data Tracks US Super CD Games
Bonk III - Bonk's Big Adventure
Cotton - Fantastic Night Dreams
Dragon Slayer - The Legend of Heroes
Dungeon Explorer II
Dungeon Master - Theron's Quest
Fantasy Star Soldier
Forgotten Worlds
John Madden Duo CD Football
Lords of Thunder
Might and Magic III - Isles of Terra
Prince of Persia
Riot Zone
Shadow of the Beast
Sim Earth - The Living Planet
Super Air Zonk

Interleaved Data and Audio Tracks US CD Games
Cosmic Fantasy II
Magical Dinosaur Tour
Valis III

Two Data Tracks US Super CD Games
3 in 1 DUO Demo CD
4 in 1 Super CD

Single Data Track US CD Games
Final Zone II
It Came from the Desert
Lords of the Rising Sun
Splash Lake
Valis II
Ys Book I & II
Ys III - Wanderers from Ys

Single Data Track US CD/Super CD Hybrid Games
Sherlock Holmes Consulting Detective Volume II
Syd Mead's Terra Forming

Single Data Track US Super CD Games
Beyond Shadowgate
Camp California
Dynastic Hero, The
Exile II - Wicked Phenomenon
Meteor Blaster DX
Shape Shifter (98 Tracks!)

Data Only US CD Games
Addams Family, The
Bikini Girls
Hawiian Island Girls
Local Girls of Hawaii, The
Sherlock Holmes Consulting Detective can inform you of the proper CUE sheets for every CD game, US or Japanese.

Even if you have a Turbo Duo, you should still keep the BIOS images for the Super System Card on your Turbo Everdrive.  You can load the BIOS image into the Turbo Duo to play CD games without having to remove the Everdrive.

Getting into a PC Engine Duo requires using a T10 Torx Security bit, a Turbo Duo requires a 4.5mm gamebit, which is also used with the SNES and N64 consoles and Genesis cartridges.  Inside the CD systems are five potentiometers marked VR101-105.  You can use a small screwdriver to adjust these if the drive is not spinning or CD audio is not playing.

Video Output

Unfortunately, no Turbo console outputs anything better than composite video.  Despite their limited 512-color palette, the Turbo consoles could put out some very colorful images and do not generally look their best with composite.  Fortunately, Hu6260 GPU outputs all the signals needed for RGB and S-Video.  There are many mods, and all require obtaining these signals from the chip itself or the expansion connector.  The PC Engine Duo I have been testing has an RGB mod from a Japanese seller called doujindance.  His mod is passive and very small.  The 5-pin AV DIN is replaced with an 8-pin DIN, with the extra lines being wired to R, G and B.  Sync is taken from the composite video pin.  This mod retains compatibility with existing composite video cables.  Other mods convert RGB to component video.

RGB looks quite superior to composite video, especially in games that use 320 horizontal pixels rather than the more common 256 horizontal pixels.  However, with the RGB amplifier in my system, one can see jailbars in the image that are not present through the composite output.  Jailbars are alternating patterns of light and dark across the screen and they are quite obvious in some games but not in others.  Bonk's Adventure is a game where they are immediately noticeable.

Save Game Backups

HuCards typically used passwords for saving, but a few Japanese supported the Tennoke 2 Backup Unit.  This device plugged into the back of a PC Engine's expansion port.  The Turbo Duo implements 2KB for game memory saving.  Many Turbo CD games only require a fraction of this memory, but some may require most or all of it. Multiple saves can be stored in the system, but there is no real way to transfer saves off the internal memory.  This 2KB SRAM chip is not battery back but instead is kept energized by a large capacitor (I have read the Duo-R has a lot more RAM).  The SRAM will completely drain the capacitor in approximately two weeks if the console is not turned on in that time.  NEC made the Tennokoe Hu-Card to backup saves from the unit.  This device appears to use flash memory, so you don't have to worry about the battery dying.  The current Turbo Everdrive does not support backing up the internal memory, but the next one may).


  1. Hi! Help me to understand why PCE CD Rom ISOs wouldn't work on an everdrive:

    Correct me if I'm wrong, but the way I understand the CD games to work on the PCE is to load their data (in batches) onto the system card (HuCard) and then have the system read from the system card the same way it'd read from, say, Keith Courage. In other words, the system card doesn't point the "system proper" to the disc drive in order for the system to read from the disc directly. Instead, the CD "feeds" the system card, and then the system just interacts with the card like normal.

    So, the Arcade CD-Rom2 card, then, is not some kind of RAM booster for the system itself, so it can better handle the disc, as this article implies. The system doesn't need extra RAM since unlike the Genesis and SNES (which can only read from RAM) it can read straight from ROM. Therefore, RAM doesn't really matter, at least not in the way it matters for SNES/Genesis, or heck, even for modern PCs (my understanding is that the Neo Geo also works this way). The CD writes to the card, yes, but in terms of how the system "sees" and interacts with the ACDR2 card, it's just a giant ROM. In fact, in terms of "ROMs the system 'sees'", it never even "sees" the disc. It "sees" the card which is in turn, "fed" by the disc.

    This is also why it's improper to say the ACDR2 "enhances" the standard base PCE hardware, but simply "liberates it", "gives it room to 'breathe', to 'fly'" rather than the strangulation and hobbling of monster hardware that we more commonly see in the teeny tiny, mapperless ROMs of the HuCards (other than SF2CE). So the Garou Densetsu Special ACDR2, for instance, is not running on "boosted" hardware, but on a "boosted" ROM on standard hardware. If that's the case, as I believe it is, then that tells us that we've SERIOUSLY underestimated the raw power of the circa 1987, technically 8-bit hardware, and there is an absolute beast lurking inside "the little engine that could".

    So, if all of this is true, then I see no reason why a CD Rom game couldn't work from the everdrive SD slot since the system is going to be looking for the game on the HuCard anyway, and not the CD tray. I don't know, maybe you would need to program the "load spots" into the ROM, so it doesn't try to load the whole game at once. But unless you can demonstrate for me that I just have a complete misunderstanding of the relationship between PCE and PCE CD (which I am open to seeing) I am having a hard time seeing the problem here.

    If the everdrive doesn't have the memory capacity of an ACDR2, then I can see how ACDR2 games wouldn't work. And I also acknowledge that just like you'd need an actual Supergrafx with its second GPU in order to play Supergrafx games on the drive, you'd still need the actual CD add-on (or TurboDuo) present since some games use large ADPCM sound files (like voice clips during battle sequences or whatever) and those are all handled by an extra sound channel in the CD system itself (the ONLY thing CD adds to the hardware proper!)

    So no, you and an everdrive, and a plain Jane TG16 are not gonna be playing Double Dragon 2. But if all the requisite hardware is present and accounted for, then I see NO REASON why a CD-Rom2 ROM or even a SuperCD-Rom2 would not work on an everdrive.

    So help me out here! What am I missing? Why don't CD Rom games work if, assuming my hardware analysis is correct, they should work beautifully?


  2. I am not sure how capable the latest Turbo EverDrive (2.4) is, so I do not know whether it would be even possible to try to emulate the CD interface. If it were, I'd be all over it.

    The CD seems to be something of a simple device, adding 64KB of work RAM, 64KB of sample RAM and the ADPCM chip. The CD System Card adds the BIOS and the Super CD System Card adds the BIOS and 192KB of extra work RAM.

    Unlike the Turbo EverDrive v1, the Turbo EverDrive v2 has at least 1MB of RAM instead of flash memory, so emulation becomes a little more feasible. I do not know how flexible the RAM addressing is, or whether the EverDrive has the logic blocks available to emulate the ADPCM chip or the streaming CD audio.

    If you compare the pinouts for HuCard connector and the Expansion Connector, you will find that all or almost all the signals you need for the CD expansion can be found on the HuCard connector :

  3. Thanks for the reply!!! :-)

    Emulating the CD-Rom is an interesting question. But my question is not about emulating the CD-Rom. My question assumes one is using either a Turbo Duo, or that the CD-Rom add-on is physically present.

    My question relates more to the relationship between the PCE proper, the system card, and CD drive. Unless my understanding of the relationship is totally wrong, the system doesn't look to the CD-Rom directly. Instead, other than the ADPCM channel, the PCE pretty much ignores the CD-Rom, but only reads from the system card as if it reads any Hu-Card. Instead, the CD interacts with the system card and fills it with the data for the system to then interact with. In other words, as far as just the actual internals of the PCE itself as a stand-alone device is concerned, there's no difference between Lords of Thunder and Legendary Axe.

    Also, my understanding of the relation between the extra RAM in the Super CD-Rom2 and Arcade CD-Rom2 cards with the system is ---NOT--- one of a RAM boost for the system, but rather as a giant ROM for the system to read......once again.......just like any Hu-Card.....only much bigger.

    So ---IF---, (and I said "If") I'm right on both of those points, and -IF- a physical disc drive is present, then I'm at a loss to see what the challenge would be in simply putting the CD ISO on the SD card and pointing the Everdrive to it, especially if the system is looking at the Hu for the game, rather than disc drive anyway.

    So, why wouldn't this work? Even if I'm wrong, and it does look to the disc drive, all someone would have to do, I'd think, is write a disc that simply redirects back to the SD card and we'd be good.

    Anyway, if this wrong, please help me see why it is and help me understand why we'd need more than just an ISO on an everdrive in a system wth a CD Drive present to play a CD game.

    Thanks!!! :-)