The system works well enough to run
over a wide range of Athlon XP CPU speeds, keeping the CPU temperature
below the 85°C maximum. This is a very positive result. Even the current fastest XP, the Athlon XP-3200+ w/Barton core, can probably be cooled well enough with this setup: Its heat dissipation of 76.8W would mean a max temp rise of 47C. In a 22-23°C room, the max CPU temp would then be ~70°C -- still well below the 85 °C max.
(Editor's note: The 41°C temperature rise with a 68.3W CPU is obviously higher than the theoretical calculation, presented earlier in the article, of a 36.4°C rise for a 80W heat source cooled by this heatsink. This is due to unavoidable losses in the heat transfer between the CPU and the heatsink.)
The noise level of the CPU cooling system is virtually nil; the only significant noise in the system comes from the the power supply and hard drive. As expected, the hard drive is the biggest
offender, and I often turned the system on and off without the hard drive connected just to "hear" the system.
ANALYSIS & CONCLUSIONS
The only part of the cooling system that became too hot to touch
sometimes were the copper blocks mounted on the CPU. During the
load tests at 2 GHz, these could be touched for a few seconds, while the
rest of the components could be touched for longer periods of
time. The copper blocks at the cooler end of the heatpipes were
able to be touched during the testing, and were noted to be somewhat
cooler than the hotter end. The large heatsink was always warm,
but a hand could be placed on them almost all the time.
I also tried aiming a floor fan at the large heatsink to see what
effect this would have on the CPU temperatures. During a load
testing, the CPU temperature was approximately 5°C lower than
without the forced air blowing on the heatsink. This was a rough
estimate to gauge the performance of the heatpipes. If the
temperature had not dropped, then this would have indicated that the
heatpipes were a limiting factor in cooling. Therefore, the
temperature could be even lower if design changes were made. These
could include increasing the surface area of contact onto the large
heatsink, improving surface finish smoothness and fit, using only the
highest performance thermal compound, making a vertical tunnel for
airflow over the heatsink, and increasing the size of the large
heatsink. There are many ways to modify this system, but the
existing system has proven to function very effectively at both reducing
noise and cooling the CPU in a passive manner.
This design works well for normal usage, and most likely even for
extended gaming sessions. The only things necessary for a complete
quiet system would be to silence the hard drive, use a passively cooled video
card, and a very quiet or passively cooled power supply.
Use you own imagination about how to physically integrate drives and a power supply to this system.