cooling
Intel® Pentium D® space heater 840
In March of 2007 I built a file server for ELK Lighting, Inc. The server was built from a bare bone kit purchased from Global Computer Supplies, a subsidiary of Systemax, Inc., and it seemed like it was going to be the right system for the job. The job was to build a 1.5 terabyte file server with consumer hardware components. I spec-ed out the hardware for the system and placed the order after approval was given.
The processor that came with the kit was an Intel® Pentium® D 840 which comes clocked at 3.2 gigahertz. I found a heat sink that advertised that it would cool the processor. The heat sink purchased was a Thermaltake TR2 M21 RX which is part of Thermaltake’s bargain cooler line. However, the bargain line doesn’t dissipate enough heat. The M21 RX is advertised to dissipate 115 watts of heat. The 840 puts out a whopping 130 watts1; which is nice if you’re looking for a small space heater. I didn’t realize at the time that the TR2 series is the bargain offshoot of Thermaltake. I previously had very good experiences with the Thermaltake brand and therefore had no reason to question this product.
The system is mounted inside a 3U rack mount case. This means that vertical clearance is limited. Most of the heat sinks I saw that said they’d cool an LGA775 processor clocked at 3.2GHz were much too tall with heat pipes galore. I’m sure they would have done the job, but that would have meant that I needed to either cut a vent in the top of the case or leave the top off completely. This isn’t an option because we need to keep dust to a minimum.
The 840 processor is based on Intel’s 90 nanometer fabrication process. It also happens to be the highest clocked processor in that line. This means that of all the other 90nm Pentium D’s this one is the hottest. The 840’s maximum operating temperature is 69.8 degrees Celsius. I have seen mine hit 72°C just by opening Internet Explorer. Anything above 70ºC and the processor begins to drag. It begins to modulate the core clocks, reduce the clock speed, to reduce power consumption and thus heat dissipation. Luckily, sharing files over a network requires very little processing power. However, rebuilding a RAID 5 array on the other hand requires a lot of processing. A 1.5 terabyte array requires roughly 20 hours to rebuild a single 500 gigabyte drive. Keep in mind that this is utilizing a soft-RAID controller and not a dedicated hardware RAID controller card.
Regardless of what I did a year ago, I am in the market for a good 130W or better heat sink. If you know of any that would fit in a 3U case, let me know. I advise that next time you’re in the market for a processor, check out the spec sheet and see if the cooler you chose can handle it.
Pentium® and the Pentium® D logo are registered trademarks of the Intel® Corporation.