Here we go... first just a quick backstory. I got this KI2 PCB probably 15 or so years ago, but it didn't work. I noticed that it was a conversion, but was missing the conversion HD interface PCB. So I planned to deconvert it to KI, but shortly afterward found a (dedicated) KI2 PCB, and this board got buried in my PCB stash. Fast forward to 3 years ago, someone was selling a conversion HD interface PCB. I grabbed it, and of course was curious how it worked... so I quickly mapped it out. Then I lost interest, and never dug out the KI2 PCB to mate it to.
Fast forward (again) to this week - I was digging through some boards, and came across my KI2 PCB. Turns out it was also dead (lifted CPU pins), but once I resoldered the CPU, and married the conversion PCB to it, everything worked (including the original 420MB Seagate KI2 HD in its plastic shell).
Now, to the interesting stuff. I remembered when I mapped out the conversion board, other than having a CPLD on it, it appeared to just pass the IDE signals through. So, I suspected (and still suspect) that the CPLD is just an auxiliary device on the IDE bus that responds to a certain set of commands that the IDE drive itself doesn't (or maybe at a different address, or slave instead of master, etc). The CPLD only has a subset of the entire IDE interface connected to it (8 data lines plus some control lines). So, I decided to try running KI (original) with the KI2 conversion PCB installed, and as I somewhat expected, it worked! Presumably, KI just doesn't talk to the conversion PCB, so it just sits there idle.
That told me that I could swap KI/KI2 by just swapping the HD, boot ROM, and sound ROMs. This makes a fairly straight-forward multi. The ROMs are 27C040s, which can easily be doubled to 27C080s and have their upper address switched. I burned both "Any IDE" images to a 27C080, and used the 4MB/8MB jumper to switch between them. Switched to 4MB pulls the EPROM A19 high (KI2 in my case), switched to 8MB switches it (presumably) to an actual address on the CPU, which seems to always be low (KI) - if making a real kit, I'd suggest actually switching it low instead of using the address though.
The HD can be run from CF w/ a CF to 44 pin IDE adapter, and I knew switching CFs was possible from my old Multi Konami Viper project (
https://forums.arcade-museum.com/th...xing-konami-viper-switching-multi-mod.432261/ ). The Viper was a bit more complicated, because it wouldn't work with SD to CF adapters (I think it ran in Memory mode instead of IDE mode). Since I had some SD to CF adapter parts leftover from the Viper experimentation, I tried it on the KI board, and it did work. 2-way SD card switches are readily available, while multi CF boards just have both CFs set up in a master/slave configuration, which isn't what we want (why I built the custom switch for the Viper). I manually toggle the SD switch, though you could add your own common control line between the SD switch and the EPROM A19s (need to check I/O voltages though).
For the SD to CF adapter, I used the CF Type II adapter with a Micro SD adapter, since it's taller and lets the switch stick out over the top of the CF socket. I also had a Micro SD to CF adapter, but it's a Type I adapter with the socket out the side, which is flush with the CF socket (so the SD switch couldn't stick out). Then it was just a matter of imaging the KI and KI2 images to SD cards. The adapter worked fine with 2GB and 8GB cards that I had laying around.
Parts I used (maybe not exact models, but look the same):
https://www.amazon.com/dp/B07KTYQRL9
https://www.amazon.com/dp/B01MY139K4
https://www.amazon.com/dp/B001DKO7R8
I used what I had on hand, but some alternatives would probably work. A CF adapter with the Micro SD socket out the back instead of side should work fine. Also, an IDE to SD adapter would probably work (like:
https://www.amazon.com/dp/B07QNB6QLC - requires a 44 pin IDE cable).
Note: I haven't switched my sound ROMs yet. I'm not sure if I'm going to keep this mod, so I didn't want to make any mods to the PCB. You can simply bend pin 1 of each EPROM and tie them to the switch... or you can remove the 0 ohm SMT jumpers, tie them together, and connect to a switch (would look cleaner). The game runs fine with the wrong sound ROMs, though most sounds are horrible screeching sounds (still says "Killer Instinct" though).
Limitations of this mod:
-The biggest one... still requires the fairly rare KI2 conversion PCB.
-Requires some wiring (SD card and EPROM selects), and ideally an MCU or something to switch the game by holding start buttons or something (not having to open the cab to access the PCB).
-Seems to require a power cycle to switch games. It hangs at boot if you switch while simply pressing the reset button. I didn't track this down - it might be something with the PCB or protection circuitry that doesn't get reset... or it might be something simple like the SD adapter just doesn't like the SD card being switched while powered. In which case, a dual CF switcher might be the solution. Switching back to the original game does work... i.e. KI (works) -> reset -> KI2 (hangs) -> reset -> KI (works) - so it doesn't get in too weird of a state.
Nice one
@DogP — a (literal) game changer for sure
Haha... good one!
DogP