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DOOM for Intellivision gameplay video


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For single player, I imagine you would use all 64 GRAM for a bitmapped screen of 64x64 pixels (8x8 characters) or perhaps 80x48 pixels (10x6 characters). Assuming you can DEFINE VARPTR using 16-bit JLP RAM, there is enough memory for calculating the graphics (256 words = 512 bytes), but then there is the limitation that you safely can only redefine 16 GRAM at vertical blank which I'm not sure how to do without a lot of tearing over four frames.


Of course there are other wireframed maze games with 90 degree turns, including entries in the IntyBASIC contests but that is not the same as DOOM. The fact that a maximum expanded VIC-20 can pull it off is a lot due to its video memory is shared between CPU and video chip so it has 5K directly available to both and I would assume a bit of clever programming which characters to redefine. Perhaps the same could be done on the Intellivision, that you don't have to send the entire character set of 64 GRAM on each frame, only those where there is a change to the picture.

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