Re: [stella] why -68?

Subject: Re: [stella] why -68?
From: "Eckhard Stolberg" <Eckhard_Stolberg@xxxxxx>
Date: Wed, 7 Nov 2001 19:05:56 +0100
What do you mean by "but"? From my experience looks like HBLANK ends at
colorclock 66 instead of the documented 68. If this is correct. when I
position an object (having it´s delay in consideration)  to be displayed in
colorclock 66, or , let say, 159 (since I´m not too sure about moving
limits), would this two pixels be visible? Mmm... maybe just giving the
background a different color from the playfield would be enough to see this.

This is not quite correct. HBLANK doesn't end at colorclock 66,
this is just the first position where you can hit the RESxx
registers (cycle 22). One cycle later would be 3 colourclocks
later which is already one pixel into the visible display. If
you position a player at pixel 159, then one pixel will be visible
on the right border of the screen and 7 pixels will be visible
on the left border of the screen. During the 2 colourclocks after
cycle 22 there is no display.

I would be very interested in hearing more on that subject...

Ok, after trying out that binary on the Cuttle Cart, I'm not
so sure anymore that the screen should jitter. It seems that
there is a bug in z26 that caused the jittering and another
bug that stops the jittering in the newest version.

It has to do with something that Thomas reported a while back.
If a STA WSYNC starts at the end of a scanline so that the
write would actually happen at the start of the next scanline,
then z26 doesn't always skip the extra scanline as it should.
But I think I know where to look for the bugs now, so that
we hopefully can fix them both and get the same result as
we have now again. ;-)

Ciao, Eckhard Stolberg

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