Silencing a P4-1.6A oc'd to 2GHz

Do-It-Yourself Systems
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What About Noise?

When first assembled, the system had 3 sources of noise:

  • Original Intel retail P4 HSF at 12V
  • Panaflo 80mm fan at 5V (over video card and motherboard chip)
  • Seagate Barracuda IV 20G hard drive ( suspended)

The PSU, as mentioned, was initially installed without any fans.

The system was fairly quiet, but far from silent, certainly noisier than my reference systems. The original Intel fan was by far the noisiest component, with a whine typical of smaller fans. Dropping the feed voltage to 5V by using at IDE power connector made a huge difference.(See this article if you don't know how to get 5V for your fan.)

I then made a change that increased the noise: I added a Panaflo 80mm fan at minimum speed to the SH power supply. Perhaps I was overly cautions; I was not comfortable with the heat I could feel rising up from the PSU through hole in the top of the case. Perhaps it was perfectly safe, but unlike silent PC pioneer Cub Lea I was not ready to do this.

The Panaflo went in easily. The little tabs on the 2-pin connector that came with the Panaflo had to be cut away, but then I was able to plug it into the pin connectors on the fan PCB. The cover went back on, and the PSU mounted normally with the opening for the 2nd fan over the CPU area.

With the thermistor in the PSU repositioned for minimal heat exposure, the Panaflo fan gets just under 5V. Enough to start, but inaudble beyond about 2-3 feet (depending on ambient noise and your hearing). It reduced the temperature of the exhaust air from the PSU from hot down to merely warm.

Before & After

I decided to record the before and after sounds with the Windows sound recorder, using a SBLive! sound card and and a cheap microphone. The mic was placed on my camera stand & positioned about 10-12" away from the CPU. 44KHz 16-bit mono quality was selected. After the recodings were made, they were converted to MP3 format to reduce the file size, down to around 130kb from the orignal 1.3 to 1.5 mb.

  • For the before setup, I put both original fans back in the SH power supply and ran everything else normally, including the hard drive.
  • The after setup was the single Panaflo fan in the power supply at 5V, both HSF and extra fan at 5V, and the hard drive suspended in elastic.
  • A third PC noise was recorded, albeit, not very successfully, because it is too quiet for the resolution of my recording gear. Much of the "SHHHH" sound in this file is simply electronic noise coming from the mic preamp circuit in the sound card. In reality, the difference is that the reduced noise P4 is always audible while the reference system is essentially silent and can only be heard late at night when ambient noise is at its lowest.

Clicking on each of the 3 speaker / sound images below should enable the MP3 files to play. Ajust your speaker volume up whne playing the first file, then do not adjust them again in order to get a sense of relative loudness.

Stock P4-1.6A System, HSF & PSU fans on normal.

Modified 4 1.6A System, HSF fan at 5V, PSU fan replaced with 5VPanaflo, hard drive suspended.

Virtually silent reference system**, mic placed 4 inches from top front panel.

** Virtually silent reference system: P3-550 oc'd to 733 via FSB, lowered VCore (1.45V), GlobalWin VOS32 heatsink w/o fan, generic PSU w/ fan @ 4V, one back panel Panaflo 80mm fan @ 4V, Seagate Barracuda IV HD in novibe style mount, generic 18" ATX case, well damped w/ highest density carpet underlay foam. This system is only audible in the wee hours of the morning when ambient noise drops to tomb levels. It makes about as much noise as a single Panaflo 80mm fan running unobstructed at 5 volts or less.

Replacing the Stock Retail Fan

The noisiest component of the system at this point was the stock Intel fan. Even at 5V, it could still be heard, with a bit of whining and clicking noises from the bearings. Because the frame of the fan actually comprises a basic part of the heatsink mounting system, replacing it without replacing the heatsink meant that something had to physically take its place.

Here's how I did it: I cut a small piece of wood the length and width as the fan assembly, and cut out the middle. (The wood is actually a piece of a tonearm board used on the famous Linn Sondek LP12, a fact that may amuse audio aficionados.) It is slightly thinner than the area of the fan structure used to clamp the assembly down. Thus, there is less pressure on the motherboard, and less bowing. The heatsink is still on very securely; I could not twist or move it in any way after it was clamped down under the piece of wood.

Another 80mm Panaflo fan was mounted over the CPU heatsink. It, too, runs at 5V off an IDE power connector. This is essentially inaudible.

Conclusion

This article posed the question: Can a Pentium 4 be made to run silently at 2-Ghz using non-exotic, inexpensive techniques? The answer is a surprising and resounding YES!

  • Running at 2 GHz, this P4 system is fast and stable.
  • With the case closed, the system is close to inaudible. When one's head is brought within 2-3 feet of the front panel, the Seagate drive becomes just barely audible.
  • Because the themperature monitor in the MSI motherboard is not functional, I cannot provide any temperature data. However, I can report that at 2 GHz, the system is perfectly stable, and the CPU heatsink rarely gets more than warm to the touch.
  • The fan over the video card and motherboard chip can be turned off with little or no consequence, which leads to a very tiny decrease in noise. The extra insurance of this fan may be worthwhile.
  • The total cost of this fast and silent system, built in late Febrary 2002, was about $825 Canadian. This is equivalent to about $520 US or $588 Euro.
  • The temperature in the room where the system has been tested has rarely exceeded 22C. It is possible that warmer weather may require additional cooling. A 5V / 12V switch might be a useful addition for the fans in this (or any other quiet) system if it must face ambient temperatures above ~30C.

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