Xref: news2.mv.net comp.os.msdos.djgpp:8320
From: phodder AT pncl DOT co DOT uk (Philip Hodder)
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Need help:  Allegro & UniVBE
Date: 5 Sep 1996 21:37:10 GMT
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References: <322D21F1 DOT 46A5 AT ohio-state DOT edu>
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To: djgpp AT delorie DOT com
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In article <322D21F1 DOT 46A5 AT ohio-state DOT edu>, kelsey DOT 14 AT ohio-state DOT edu says...
>
>I just installed the newest version of UniVBE on my computer...  I've
>been trying to write a tile-based game in 640x480x256 using Allegro
>(involving a lot of bitmap-blits and page flipping...)  I've notice that
>the tiles scroll up and down a lot faster as long as their top corner
>has an X value that is a multiple of 4.  Why is this?  How can I make
>the whole thing go faster (or *ugh* slow the whole thing down) so it
>will scroll at a constant speed?  I didn't have this problem before
>installing UniVBE.
>
>Thanks,
>Bart

I believe that's mentioned in the ALLEGRO.TXT file. However it does say - 
oh, hell, I'll cut and paste! Here 'tis:

   Mode-X scrolling is reliable and will work on any card. Unfortunately a 
   lot of VESA implementations (including UniVBE!) can only handle 
   horizontal scrolling in four pixel increments, so smooth horizontal 
   panning is impossible. This is a shame, but I can't see any way round it.

Doesn't say WHY exactely - I'd guess it's how UniVBE deals with memory. 
Vertical scrolling should be OK (?)

I don't know if there's a workaround - I suspect not.

HTH,

Phil.