> Does anyone have any experience with NetBSD running on a 264DP
> motherboard?

Not with exactly that motherboard, but with its distant cousin,
which sits in an API CS20 (a closer cousin would be the DS20).  I
beleive these all use the same chipset, though.  Unfortunately,
my CS20 gave up its spirit a while ago, so I no longer have an MP
alpha running, but when I had it in operation it worked just fine
and was quite stable.

I don't think there are any limitations on the amount of memory.
The Alpha port was among the first ones to get MP support in
NetBSD, so "anything newer than or equal to 2.0" should be OK
(not that I would *recommend* 2.0 especially now that 2.1 is
out).  If you feel uncomfortable trying to run 4.0_BETA2, I think
I would recommend 3.1 or 3.1_STABLE.

Regards,

- H=E5vard