- 4MB RAM (I wanted socketed memory, so eight 512Kx8 SRAMs)
- 1MB Flash (to boot the cart, 2x Am29F040)
- USB interface for quick "assemble-then-test" cycles.
- IDE interface for a Compact Flash to IDE adapter, to load games^H^H^Hhomebrew programs into RAM.
- Banked SRAM support for PSIV and others. I won't support SSF2 banking or the SRAM write-enable bit though, just A130F1 bit 0 is implemented currently.
Ramtron is discontinuing their 5V parallel FRAM products and NVRAMs are really expensive, so I think I'll just have to use battery backed SRAM for savegames. The battery part isn't done yet, but after that the cartridge will be finished. I haven't had the time to play RPGs for some years now, maybe it's not important to add this.
![Crying or Very sad :cry:](./images/smilies/icon_cry.gif)
I've found that I have a lot of room left on the board and want to add some perhaps crazy things. The board is already huge so why not make it even bigger?
![Very Happy :D](./images/smilies/icon_biggrin.gif)
Currently I'd like to put a 68EC000 @ 20 MHz with 512K or 1MB of local RAM on the board as a coprocessor. I bought a lot of 16K dual port RAMs for cheap that would greatly simplify communication between the Genesis 68000 and the coprocessor. I suppose it could do things like sprite collision processing or other tasks, maybe mix some audio channels together into a buffer in the dual port RAM for the Z80 to send to the DAC.
But I wonder, are there any really useful things for a coprocessor to do? I never felt the Sega CD 68000 improved anything, other than freeing up the Genesis from having to poll the CD and PCM chip. There aren't any CPUs available that could have SVP-like performance, so I'm not planning on polygons -- but I'd love to see what kind of wireframe graphics could be done instead.
Assuming the 68K would edit bitmaps (scaling, software sprites, etc.) in local memory before transferring to dual port RAM to be DMA'd to VRAM, I designed circuits for packing/unpacking nibbles into bytes and a 32X-like overwrite feature. But after crunching some numbers I don't think the 68K could really push around enough data to be useful at 20 MHz. So it seems less likely that the coprocessor could generate a whole 256x192 frame of data at 30FPS.
![Sad :(](./images/smilies/icon_sad.gif)
Anyway, I'm not decided on what to add, if anything. What would people dream of having? What would you add if you were a Sega developer in the 90's? (no PowerVR or FPGA or MP3 player, please)
![Wink ;)](./images/smilies/icon_wink.gif)