On 13/10/2016 15:28, Gerrit Heitsch wrote: > How much of it is spent in the upper and lower border and the vertical > retrace where no memory access happens (not counting an open border > with sprites)? More than 2 ms? > > So in order to make sure that the DRAM is refreshed properly, they > just implemented a refresh counter which does 5 cycles per scan line. I thought upper/lower border was always fetching $3fff? During the side borders it's fetching sprites, so you can't rely on that for refreshing Doing 5 refresh cycles per scanline will take 51 scanlines to read all 256 addresses. After 51.2 scanlines the VIC should have read all 256 addresses, just by character fetches. I doubt they thought they'd better put a separate dram refresh in case someone figures out how to mess up the character fetching (duplicating rows/vsp etc). There must be another reason. Message was sent through the cbm-hackers mailing listReceived on 2016-10-13 19:00:02
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