Jorge Chamorro Bieling wrote:
You see it as: "Standard memory is cheaper, and there's a way to go with it". And then you're right. still... hmmm I see the dual-ported ram design as bright and clean, and the other as a pain to suffer because the dual port ram happens to be so expensive.
I agree, the dual-port idea is much less painful. But that means large (== expensive) FPGA or some external DPRAM which also increases the minimum I/O count of your chosen device.
I don't know much about A2 hardware, but a colleague mentioned some vague recollection he had about doing 'tricky' things with A2 graphics timings to get 'special effects' (he couldn't give me anything more concrete than that). I'm assuming he's talking about updating A2 video RAM at strategic points in time to get undocumented behaviour...
If this is indeed the case, you're going to lose that capability if you're 'screen-scraping' the A2 video RAM completely asynchronously. IIR I do notice that Slot 7 has the VBLANK/VSYNC signal on it. But that my not be enough...
FWIW, if you're going to stick a *large* FPGA on it, you may as well include a cheap USB host chip, some (more) RAM and CF adapter. That way you can make a multi-function card which does VGA, takes USB keyboard/mouse, has extra RAM, and Compact Flash.
For all the talk about how difficult it would be to create an 8-bit micro 'USB card', if you only want keyboard/mouse, it would be trivial to get, say a Cypress USB host chip, and write firmware on the chip to talk to a HID USB keyboard, emulate the A2 keyboard chip in the FPGA - no A2 driver software necessary.
Regards, Mark