[stella] Overscan & Vblank confusion...

Subject: [stella] Overscan & Vblank confusion...
From: Manuel Polik <manuel.polik@xxxxxxxxxxx>
Date: Wed, 07 Mar 2001 11:25:46 +0100
Eckhard Stolberg wrote:

Huhu Eckhard!

> One thing that you should add when you clean up your code are some
> instructions that turn on VBLANK at the start of the overscan. If
> VBLANK isn't on during the VSYNC lines, you'd get a strange gloom
> at the top of the screen. At least on a PAL TV where the displayable
> area is bigger than the display of your game you would.

Now, you may have noticed that I did what you suggested already some
time ago, but after more & more thinking about it, it now doesn't let me
sleep anymore.

After I did that, I end in fact with a vertical blank that consists of
the overscan + the normal vertical blank.
Or, saying it differently: VBlank is eating up the overscan time too,
actually I'm not doing an *overscan* as such at all, right?

So why then making a difference between overscan and vblank at all?

I could just set up a timer big enough for all overscan & vblank lines
to do and just blank it all the time?
(What timer value would I need for that BTW?)

Wouldn't that automatically help Andrew, too?

Or am I missing something right now?


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