At 19:03 21.09.99 -0500, you wrote:
>I am uncertain about why the first three STA WSYNC's are there.
One of them is to make the access to VSYNC happen at the start
of a scanline, so that you get a VSYNC signal of three full
scanlines. The other two: well I suspect that Atari's programmers
first used screen loops with register counters for 256 scanlines.
You would need 6 more lines to get the suggested 262. When they
started programming real games, they pasted the working VSYNC
routine in the code. And Nick then copied the routine from one of
Atari's games. They are actually unnessesary
>Should not the 30 counter in the overscan be changed to be 27 for correct
>scan lines?(or the WSYNC's in verticalblank be removed) Did I miss
>something?
This might be true. If you have the Stella emulator for DOS, it shows
the number of scanlines for the last completed frame after you exit it.
you can use this to find out how many scanlines your programs actually
do.
>Is this an accurate replacement? As in, does it take up the same number
>of lines?
Yes it is.
Ciao, Eckhard Stolberg
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