I have been running  NetBSD-1.5->1.5Y and XFree86-4.0.2 on several
single PCI bus alpha's which include:
as433au,600au,alphastation 600,as800 and as1000a -running since last
April, very successfully and with great -netbsd stability. What makes
NetBSD heads above the rest is a great pkgsrc collection where
everything platform supported, actually can be installed! (out of the
box). You can get the xsrc distribution i use from :
http://www.caseydoodle.com  ,Supported video cards that i know work are:

Elsa Gloria -permidea chip or older 3DLabs chips
Matrox Mystigue , these are the only cards i have been successful with.
A custom kernel with wscons support is required e-mail me off the list
for kernel config file and /etc file changes.
-Mel