Re: [stella] Weird timing bug, I!

Subject: Re: [stella] Weird timing bug, I!
From: Adam Thornton <adam@xxxxxxx>
Date: Sat, 20 Apr 2002 15:02:13 -0500
On Sat, Apr 20, 2002 at 07:58:38PM +0200, Thomas Jentzsch wrote:
> I don't know why it works on SC, but I think there is a problem with
> VSYNC. Your code (@Manuel: availabe at AtariAge :-) looks like this:
>     lda #2          ;bit 1 needs to be 1 to start retrace
>     sta VSYNC       ;start retrace
>     sta WSYNC       ;wait a few lines
>     sta WSYNC
>     lda #44         ;prepare timer to exit blank period
>     sta TIM64T      ;turn it on
>     sta WSYNC       ;wait one more
>     sta VSYNC       ;done with retrace, write 0 to bit 1
> The problem might be, that you don't do 3 full lines of VSYNC. The first
> WSYNC happens (according to z26) after about 1/3 of the line. Then you
> are doing two more WSYNCs. So you only do 2 2/3 lines of VSYNC, but you
> should do at least 3 full lines. Adding one more WSYNC might solve that
> problem. But I'm not 100% sure.
> Did you change that part of code or is that original Dark Mage code? If
> it's original code, then does Dark Mage work on your TV?

I think it's original code, and I don't have a Dark Mage cart.  I'll try
Dark Mage on my Supercharger....

Same as FotR, actually. Yellow text, red background.

Now the really weird thing...Randy tried the game before he shipped it
and it played fine for him.  And I tried it again today, and today it
was readable although the background was doing this weird red/purple
pulsing color thing.

I'm guessing that it's just-a-little out of NTSC spec, and that Randy's
TV can cope, and mine sort of can, better today than it could

But that still leaves the question, why does the SC behave differently
than the ROM?


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