I'm in the mood for a homebrew computer. I've been ruminating on the idea of making a cheap 8-bit computer for a while. Something like Z80 + AY-3-8910 + TMS9918.
Anyway, here they are:
3x TI TMS9929A (TMS9918 but YPrPb @ 50 Hz instead of NTSC)
5x Zilog Z84C0020 (Z80 @ 20 MHz)
5x Zilog Z84C0008 (Z80 @ 8 MHz)
4x GI AY-3-8910
4x UM61512AK (64 KiB SRAM)
This is going to be a very ambitious project that I most likely won't be able to accomplish, especially considering how inexperienced I am with hardware, but here are some notes. If anyone has any suggestions or ideas to share, hit me up.
TMS9918 expects 8x 4 KiB TMS4116 as external VRAM, which is DRAM with negative voltage bias rail, but there's a neat hack I found to make it use a generic 32 KiB SRAM with some register chips. I might try to convert the YPbPr component video output to RGB VGA at some point.
I'll need to manually implement I/O logic for stuff like bank switching to let Z80 efficiently use the whole RAM whilst being able to access the ROM.
Also TMS9918 and AY-3-8910 naturally have much lower clock speeds, so I'll need to learn to do clock stretching.
