Only the last two or three models of PowerMac G5 (2.5 and 2.7GHz) had 
water cooling systems; my primary desktop is a slightly older dual 
2GHz PowerMac G5, which is air cooled. I will grant that it is the 
most massive such system I've ever seen in a consumer device, 
however, Apple was kind to its customers by using variable speed fans 
which are controlled by the thermal monitoring system. If the CPUs 
aren't being stressed, it's very quiet (not as quiet as my G4 Cubes, 
but those are 500MHz G4's with 100MHz RAM, not 2GHz G5's with DDR 
RAM...).

Most impressive cooling system I've ever seen was the flourinert 
cascade for the Cray-2 at the LLNL Magnetic Fusion Energy Computer 
Center (MFECC) in 1986. It had four 250 MHz processors immersed in 
the cooling fluid. It was both functional, and nice to look at, too.

You're correct in that all the Alpha CPUs I've seen (mostly 21164A 
and 21264) have two fairly big (0.5 cm diameter?) bolts on a copper 
cover for securing the heat sink to the CPU. If you can find the 
right kind of heat sink,how hard could it be to drill a couple of 
holes in it ... ? I specifically referenced the overclockers because 
they do all kinds of crazy things in service of their need for speed; 
if you want a silent Alpha, some of those techniques can probably be 
adapted, and there is enough of a market for extra cooling systems 
that there are vendors (e.g. Zalman, Thermaltake) who'd probably be 
happy to help.

	Erik <fair@netbsd.org>