4 ms·
It does have video RAM, at least sort of. There's about 20 registers on the graphics chip that control the display of the playfield bits and sprite objects. T
by vikingerik 4y ago
It does have video RAM, at least sort of. There's about 20 registers on the graphics chip that control the display of the playfield bits and sprite objects. They hold the values persistently until rewritten, so in a way that is functioning as video RAM, just not as a bitmap, and it holds a one-dimensional scanline rather than a two-dimensional frame.
Another way of looking at it is that the video "RAM" is actually the phosphor on the display screen, persisting each scanline when written until refreshed on the next frame.
- diydsp 4y ago> a one-dimensional scanline And iiuc it's only abt 40% of the line. You have to update it during the line! and sometimes it's fwd and sometimes bkwd so you can't simply let it repeat a simple pattern!
- vikingerik 4y agoI don't know where you're getting that from. You can indeed leave all the registers alone and it will repeat whatever is there for any number of scanlines until you do change it. In fact, this is what happens if you power up the 2600 without a cartridge - you see vertical stripes, because whatever garbage was in the registers on powerup just stays there and repeats onto every scanline, with no software changing it. "Sometimes forward and sometimes backward" would only apply to the three registers of playfield bits, and is fully controllable by software, in the CTRLPF register.
- kgwxd 4y agoI'm sure they're talking about manipulating a single line and the fact that you're extremely limited by the behavior of machine for that particular line. Anything that doesn't fit within the hardware design constraints needs mid-line changes and/or clever hacks and, even with those, what you want to output might just not be physically possible.