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homebrew videocard question?


harshbarj
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I'm still working on building a computer based off the z80. I'm now to the point were I want to get a video card. I have decided I want to use a second z80 CPU on the video card to take some of the burden off the main CPU. The question is how do I have the two cpu's talk to eachother? I was thinking of setting aside a few k of ram for video memory but if I do that how the heck will the z80 on the video card be able to read that memory (as reading that memory is all it will need to do, while the main CPU will need to read/write to the same memory). Would it be best to have ram on the videocard and find a way of writing to that? (if that can even be done)

Sadly the memory is the last stumbling block. With only 64k I can't do much (I really want to find a mmu for it to solve that problem, but no luck yet). I figure 4k ROM and 2k for video should leave me with ~58k depending on how I have to split the memory (not sure if I can set memory up like that yet). Once I get the memory figured out I'm ready to build the first prototype  :-D

I already have the ps/2 keyboard / mouse all figured out(will use a microcontroller for those to keep the CPU free for other tasks). I have a good idea on the sound card (going with a Yamaha chip from an old sound blaster). The hard drive will be simple to do(thinking of using an old 32MB cf card, or I do have an old 8-bit ide 80mb hdd in the garage) as will the floppy drive.

I think version 2 will use a z180 as it can use 1mb of ram  :shock: and is still being sold on jameco.

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