Voodoo 4/5 display problem

[jb701@uku.co.uk]

I'm using KDE, with a Voodoo 3 card.  Excellent display. 

THen I try to swap it for a Voodoo 4.  I get a crawling display [that's how 
it looks - all the pixels constantly moving]. 

I looked ona another machine I usually use without GUI - it has a Voodoo 5.  
I load KDE, I get the crawling problem. 

So it's something about debian [windows 2k looks great on these cards - dual 
booting so I know]. 

Any ideas?  Is there something I need to change? 

- Joe