I just finished building two render nodes for my little basement rendering
farm and stumbled across something of an oddity.

Machine "A" has an Abit IC7-G motherboard, 3.2 GHz Pentium 4 CPU
(hyperthreading enabled), and 1 GB of DDR400 dual channel Corsair
TWINX10243200C2PT dual-channel memory. So does machine "B". Other than the
O/S, the only software installed on machine "A" is POV-Ray for Windows v3.5.
The same is true for machine "B". In fact, both machines are *identical* in
every respect, right down to the manufacturer of the hard disk drives and
the trackball mice... identical in every way save one: Machine "A" is
running Windows XP Pro (SP1), but I didn't have an extra copy of XP lying
around when I built machine "B", so I installed my old copy of Windows 2000
Pro, upgraded to SP4.

I ran a benchmark that I've been using to test the rendering speed on my new
workstations, and over an average of 10 runs machine "A" (the one with
Windows XP) averaged 4 minutes 17 seconds. Now I always thought Windows XP
was a bit of a pig size-wise, so I thought for sure that the Win2K machine
"B" would--at the very least--edge out the performance on its XP-saddled
sibling. Wrong! The Win2K workstation was, in fact, 25% slower than the XP
machine over 10 tests... an average rendering time for exactly the same
scene with all the same settings of 5 minutes 26 seconds.

After checking the BIOS versions and other esoteric settings to ensure that
both machines really *were* identical except for their O/Ses, I went to
CompUSA and bought a second copy of Windows XP Pro which I installed on the
Win2K machine, and then I reran the benchmarks again. The rendering times
were now almost exactly the same as for the other Windows XP Pro
workstation. I'm left to conclude that, for POV-Ray and for that benchmark
at least, Windows XP Pro is significantly faster than Windows 2000 Pro.

How can this be? I thought the core processing speed that both O/Ses are
capable of was pretty much the same, and that the speed-ups in XP were
mostly in things like starting and stopping apps and the system itself. Was
this just some sort of weird fluke, or is the culprit something more subtle
like the hyperthreading processor--does it not like Windows 2000 or
something? If anyone has run into something like this before, I'd sure like
to hear about it.

Thanks...

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