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CPU Heatsink and Fan Installation Guide by Greg Cloon
As my G3 233’s birthday is creeping closer, and the CPU speeds are getting faster, I am experimenting in ways to get my Motorola PowerPC 750 chip to run a little cooler. Tempted by the claims of running the chips at up to 282mhz, overclocking seems to be a frugal short-term solution in the quest for more power. This whole "cooling" thing started after I downloaded Powerlogix Speedmeter. It is a great little program that will tell you, among other things, the temperature of the CPU. I discovered my machine was running around 135 °F. Which to me seemed a little warm. So I tried using thermal compound on the passive heatsink. This dropped the temperature about 5 ° to 7 °F. This still seemed a little warm, so I started thinking about an active cooling system.My first purchase was this great musical fan. If the fan ever quit spinning, it would start playing a song to alert me. Provided the fan was hooked to a speaker. The fan was originally designed to fit a Pentium processor, and with careful alignment it would fit onto the G3’s ZIF socket. The only problem was in my desktop case things are a little cramped. Very Cramped. With the fan in place, I could no-longer close the case. Apparently there isn’t much clearance. This probably doesn’t aid in the circulation of air inside the case either. The case actually only has one fan in it. The fan is located inside the case on the bottom of the power supply, and spends its time sucking air from the outside through the warm power supply, and then into the case. This surprised me. The little bit of air that does get into the case for cooling passes through a "heating unit" first. I will more than likely turn this around, but that will be a whole different story. My second purchase was an older, cheaper, smaller, shorter fan originally designed for a 486 CPU. The active heatsink was minimally smaller than the G3 passive heatsink, and with the fan, was about the same height.
The first "work" I needed to do was to unscrew the fan from the heatsink. The clip on the fan was larger than the G3 heatsink clip and I needed to swap them if I had any hopes of getting the active heatsink to stay on the CPU. Nothing major, the clip is under the fan and four very tight screws are all I needed to remove. The second was working the grounding screw into the new heatsink. This was just a question of delicately lining it up, and sheer brute force. Once the G3 clip was in place and I had reattached the fan to the heatsink, I reapplied thermal paste and snapped the fan into place.
For power, I unplugged the hard drive, and plugged that into the fan, and the fan into the hard drive. The power is still uninterrupted to the hard drive, now there is just two little leads coming off and into the fan. I started the machine with the case open and motherboard still exposed to make sure the fan and everything was functioning correctly. Then I opened Powerlogix Speedmeter again and the temperature was down almost 10 ° to 118 °F. I checked to make sure the fan was seated properly and noticed it could be "rocked" a little. As soon as it was rocked, the temperature would jump to 140 °F. Make sure it is seated properly.
I fired up a game of Quake with no hardware acceleration to see if I could get it to heat up a bit. After playing for a little over an hour the temperature was up to 125 °F, a small improvement from the stock heatsink. I closed the case and fired my baby back up and noticed the temperature reading was now at 132 °F. I’m a little disappointed in the results. I was hoping to drop 10 ° to 20 °F but haven’t dropped any. I am thinking a better solution is to get fresh air from outside of the case and creating a cross breeze past the processor. This would include turning the fan in the bottom of the power supply around so it blows out and mounting another fan by the PCI slots to suck air in. But, that is another story. |
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