Re: [stella] Trick to avoid black line on screen after HMOVE ?

Subject: Re: [stella] Trick to avoid black line on screen after HMOVE ?
From: Greg Troutman <mor@xxxxxxx>
Date: Tue, 18 Mar 1997 10:52:48 -0800
kingkong@xxxxxxxxxxxxxxxx wrote:
> 
> There is always a short black line at left of screen after HMOVE
> (when not done in Vertical Blank) following a WSYNC.
> 
> Some games like HERO, Decathlon and Enduro just 'skipped' the first
> two bits of PF0, so it is not visible any more. But they used the last
> two bits of the screen (on right side), so PF0 must be updated twice every
> scanline, right ? (Quite a lot of cycles wasted just to avoid this problem).
> 
> I want to use this trick, too. The thing is that PC Atari does seem
> to have problems with this type of code so I cannot test my program
> properly.
> 
> Anyone with a solution to this problem ?
> I could skip the last two bits as well, so I do not waste time by updating
> PF0 all the time, but this reduces the size of the display too much.

Hmm. I would guess that some or all of these games don't actually update
PF0, but might instead just be doing an HMOVE on every single scanline
to create the two bit margin you see.

--
mor@xxxxxxx
http://www.crl.com/~mor/

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