Re:How early 8-bit arcade machines differed in design from 8...
by tinus_hn on Tuesday October 09, 2018 @09:49AM
(#18175934)
The sprites and backgrounds use the same memory as the main CPU so more sprites and more complicated backgrounds means the CPU gets stalled more.
On the C64 for instance the first line of a character (so one every 8) is when the graphics chip fetches the list of characters on that line and that line is a ‘bad line’ where the CPU has much less cycles. And then the CPU is stalled for 50% of the rest of the time so the graphics chip can fetch the character bitmaps indexed by the data fetched during the bad line.
On the C64 for instance the first line of a character (so one every 8) is when the graphics chip fetches the list of characters on that line and that line is a ‘bad line’ where the CPU has much less cycles. And then the CPU is stalled for 50% of the rest of the time so the graphics chip can fetch the character bitmaps indexed by the data fetched during the bad line.