kyuusaku wrote:
Bump. I fooled around a little with the GAR today and can conclude a few things:
It certainly polls $4016 into a shift reg, once it gets the hotkeys it does it's thing. Games which do not do anything with $4016 (FDS BIOS) will not get you a menu.
Hmm very interesting things about the GAR. I've been wondering for awhile how it detected the mapper type and such, because it seemed to work really well for the games I tried it on (MMC1, MMC3, codemasters, other US games).
It will fully back up 8K of VRAM, since it worked OK on the codemasters games. What I had trouble with (and what will brick your GAR!) is multicarts or any mapper that uses the write address as a bankswitching element. For some reason, the GAR doesn't like it. Examples include multicarts and the action 52 and cheetahmen 2.
I tried tracing through the ROM a ways but it's an absolute mess. I did find where it jumped into RAM though, and that's how I made my GAR fixer/dumper. There's some "locks" on it you have to turn off to make RAM writable, for example.
Also, the stupid thing only has 32K of RAM in it, but was designed to hold up to 256K. I am still wondering how the menu comes up- They must be dual porting that RAM between video (probably only 1K or so for a basic CHR set) and the CPU so they can read stuff and write it to RAM. I'm not sure. Whatever they do, it's insanely complex, especially for the time period.
I suspect that the chip used in the device is designed for a famicom copier of some form, and was most likely one of the last ones to be built/designed.
Speaking of using copier chips, Naki's "gamesaver+" for the SNES is just a bung? copier chip in a device that only does real time saves for SNES. It's pretty neat and basically a simplified SNES copier inside. 256K of DRAM, the copier chip, and little else.