CPU "Back Door" Cooling

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SUMMARY: Paying attention to secondary heat sources can drop CPU temps by a few extra degrees.

As I do more heatsink testing, I am monitoring not only CPU temps but the CPU’s back and side temp core temps as well. One heat source on all motherboards are the power transistors, and I put a fan over the six of them that the ABIT KT7 features. They don’t run particularly hot (around 35C/95F) but I placed a 60 x 15 mm fan over them to see what would happen.

Top Fans

As the pic above shows, I just laid the fan over the capacitors around the power transistors and let it run. To my surprise, rear CPU temps start to fall (running Prime95, Duron 800 @ 1000, 1.93 volts)! As the table below shows, temps across the board were lower:

Condition

CPU Back Temp

CPU Side Temp

MBM 417 Temp

No Extra Fan 55.2C/131.4F 45.6C/114/1F 42C/108F
Extra Top Fan 53.9C/129.0F 45.0C/113.0F 41C/106F

I placed a probe on the back of the board, underneath the socket, and recorded a temp of 37.2C/99.0F.

Hey – this is getting interesting! So I then decide to lift the motherboard up and get some air to the back of the board in addition to the top, as shown below:

Bottom Cooling

With this added cooling, I drop back CPU temps by 2.6C/4.7F – about a 5% temperature decrease. The temp probe on the back of the motherboard now shows 29.0C/84.2F – Not bad!

Condition

CPU Back Temp

CPU Side Temp

MBM 417 Temp

No Extra Fan 55.2C/131.4F 45.6C/114/1F 42C/108F
Extra Top Fan 53.9C/129.0F 45.0C/113.0F 41C/106F
Top + Bottom Fans 52.6C/126.7F 44.6C/112.3F 38C/100F

The point of all this is that you might be surprised what a little extra air flow in the right places can do for you. Feel around your motherboard (carefully) and if you detect some hotspots, a fan directed at it might yield some unexpected dividends. These are “free” temp reductions just waiting to be found.

Email Joe


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