Two UberGROM images: Logo/Logo-II/Multiplan/TurboForth and Plato/Return to Pirate’s Isle

Thanks to Tursi, Ksarul, and a few others, it’s now possible to create bankswitched GROM/ROM cartridges for the TI-99/4A.

Most of the game cartridges were converted long ago to disk-loadable EA/5 images (most needing the 32k RAM expansion). The languages, courseware, and things that wouldn’t fit into a RAM expansion have not been converted.

The aforementioned guys built a GROM simulator around an AVR, added a bank-switching 512k EEPROM for the ROM side of the cartridge, and released it as the UberGROM cartridge board.

Therefore, I went ahead and created two multicarts. The first one contains Logo, Logo II, and Microsoft Multiplan. The second contains Plato and Return to Pirate’s Isle. They can be found here.

Update: the first image now also contains TurboForth v1.2.2.

To convert these to cartridges, first obtain two UberGROM cartridge boards. The link above goes to ArcadeShopper’s web site, but you can also purchase them directly from Ksarul on AtariAge.

The AVR must be prepared as per Tursi’s instructions here. The instructions expect you to have a cheap eBay TL866 EPROM burner, but it’s also possible to program with avrdude via SPI. Contact me for details if you decide to go this route.

Next, extract the files from the archives you downloaded from the links above. If you’re building both cartridges, extract into separate directories.

Next, burn the “eprom.bin” that corresponds with which of the two multicarts you want to create onto the EEPROM that you should have received with your UberGROM and install it onto the board.

Next, copy “cart1.tifiles” or “cart2.tifiles” onto a TI-readable media. I use and recommend the HxC Floppy Emulator, which uses disk image files on a SD card to emulate a Shugart-compatible floppy drive. Note: these files are (obviously) in TIFILES format; do the needful when copying them onto the target media.

Next, copy “gromcfg” from Tursi’s website onto the same TI-readable media. Insert that media into the floppy drive. If HxC, be sure to mount it.

Next, insert the prepared UberGROM cartridge into the TI. Hold down the space bar and turn it on. After the rainbow screen, you should see a menu that includes “Run Program”. Choose it.

The file you run will be “DSKx.GROMCFG”, where “x” is the number of the drive that contains the prepared media. After several seconds, you will see the GROMCFG browser.

Hit control-L. Say yes, you really want to do this, then feed it the name of the cartridge file (“DSKx.CART1” or “DSKx.CART2”.

Now go get a beer, this takes about five minutes.

When it’s finished, powercycle the TI. After the rainbow screen, you’ll see an option for “Multicart”. Choose that, and you’ll see the selection menu for the multicart that you just created.


About Chris Kobayashi

I'm a security systems engineer, specializing in UNIX, network, and physical security. I'm in Tokyo, and I'm mostly retired now. I'm well-versed in both electrical and software engineering, with a particular interest in old computers and game consoles. You can contact me here.
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