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  Keeping Intel's Prescott cool and quiet 
  Oct 06, 2004, 08:30am EDT 
By: Sander Sassen

Intel's 90nm Pentium 4 processor, codename Prescott, is one of the hottest processors money can buy, despite the die-shrink. To keep it running cool Intel supplies a heatsink which gets the job done in a well ventilated case, but doesn’t go about it quietly. But there’s more, besides generating a substantial amount of heat, more than any other Intel desktop processor, Prescott consumes a lot more power as well. This means that the power supply and the power regulating circuitry on the motherboard are operating under a substantially higher load. For example, if your motherboard isn’t listed as ‘Prescott compatible’ it might not be able to handle the extra load, possibly causing its power circuitry to fail or get excessively hot shortening its lifespan.

We’ve recently upgraded one of our socket-478 systems with an Intel 3.2GHz Prescott processor as well, and wanted to make sure it was as quiet as before, with little or no audible fan noise. That seemed a daunting task at first, as the 3.2GHz Northwood it replaced ran about 15 degrees cooler with the Thermalright SLK-947U, which is a high-performance all copper heatsink with a low-RPM 92-mm fan installed. But more noticeably was the fact that the 350-watt Antec TruePower power supply, the power supply used in all of our test systems, had trouble keeping up with the load. With the internal fans spinning at, or close to, maximum-RPM the power supply was now the noisiest component in our system and quite warm to the touch as well.

So we set out to quiet this system down once and for all, regardless of the amount of heat the Intel Prescott generated. Obviously a more powerful power supply was needed, but also one with a higher efficiency, so that the net amount of heat generated within would be as low as possible. And of course it had to be quiet as well, so that’s three requirements that aren’t easily combined. A power supply’s efficiency is often referred to as the power factor of a power supply. Active power factor correction is needed to achieve the best possible efficiency and the least amount of heat produced and there’s but a handful of power supplies that have this feature. Unlike passive PFC active PFC corrects the power supply’s power factor and makes sure less power is wasted when converting AC voltages to the DC voltages in a PC. The upside of all of this is that when properly implemented, active PFC is able to generate a theoretical power factor of over 95%.

Zalman ZM400B-APS

The Zalman ZM400B-APS power supply, offering 400-watts of power and active PFC.

After having spent some time with a variety of active PFC power supplies we decided on the Zalman ZM400B-APS as that offered the best combination of power, noise and efficiency. This power supply not only has a full range input, so it accepts all line voltages from 100- to 240-volts AC, but is able to achieve 94% efficiency under full load, whilst keeping absolutely whisper quiet. Don’t be fooled by passive PFC power supplies promising similar figures, as you’re not going to find that kind of efficiency with any passive PFC power supply. Actually if you’re serious about reducing the heat generated in your system, to which your power supply is a large contributor, you shouldn’t even consider a passive PFC power supply.

Thermalright XP-120

Thermalright XP-120, aluminum heatsink with heatpipes and 120-mm fan.

Now that we’ve tackled the power supply problem, we were still faced with a processor running at over 65 degrees Celsius with a high-performance heatsink. Naturally we could’ve beefed up the performance by simply installing a fan with a higher RPM, but we wanted to quiet things down remember? So the only alternative we found, that’s affordable and doesn’t use water or phase change refrigeration, is Thermalright’s XP-120. This is a rather large heatsink utilizing copper heatpipes to draw heat away from the copper base of the heatsink and transfer it to the large, fine, aluminum fins. As a credit to its name the XP-120 uses a 120-mm fan to cool things down. When we installed a 1900-RPM YS-Tech 120-mm fan we didn’t expect the XP-120 to fare much better than its copper predecessor, but we were pleasantly surprised to find that this whisper-quiet combination kept the processor well below 50 degrees Celsius, even under full load.

So by tackling these two major contributors to a system’s heat and noise production, we were able to reduce the noise production of our Prescott system down to a hardly audible hum of the 120-mm fan. That is until the cdrom spins up, or the harddisks start rattling, only then you’ll realize that the processor and the power supply are no longer the two biggest contributors to system noise of this particular system. If we wanted to quiet it down even further we’d need to remove the two 10.000-RPM Raptors and install a pair of Seagate Barracuda’s instead, but for now we’re more than happy with the result. If you’re also battling to keep your system noise, or heat production, down, do give the above components some consideration, we’re sure you won’t be disappointed, a quiet Prescott system isn’t a fantasy, although it does require some effort.

Sander Sassen.

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