A Guide to the Graphics of the Sega Mega Drive / Genesis

rasterscroll.com

53 pointsibobev6 comments

All derived from the original 1979 Texas Instruments 9918!

Yeah, Mode 5 is pretty different from any of the TMS9918A modes and it lacks those older modes (unlike the SMS VDP), but there are a number of funny details that only really make sense if you understand its predecessors. The bits in the command word are arranged strangely and the two registers that control the starting address for the background planes are laid out differently from each other.

Accolade used the TI documentation as part of their clean room reverse engineering of the Mega Drive.

Oh really, I hadn't heard that before. From doing some searching I see that elsewhere you mention that you worked at Accolade. Would be curious to hear more of the story of how that reverse engineering went down.

I wouldn't think the TI manual would be all that useful given how much changed between the TMS9918A and the Mega Drive VDP. I guess knowing what a register write looks like is a lot better than starting from zero though.

Sega Genesis had a charm that no other console has quite been able to capture.

I'm happy to see it has such a vibrant homebrew scene.

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