AOpen i915GMm-HFS: 2nd Gen Pentium M desktop board

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POSTCRIPT - AUG. 7, 2005: AN IMPROVED HEATSINK

SPCR's review of AOpen's i915GMm-HFS Pentium M motherboard found it to be a nice board hobbled by a sub-par heatsink. Not only was it incapable of cooling a 20+ watt Pentium M processor, its proprietary mounting design precluded easy replacement by any known aftermarket heatsink.

While testing this board, I had several conversations with AOpen's tech people. They were aware of this issue and claimed that a redesigned heatsink was in the works. Since nothing tangible materialized by the review deadline, the review was published using the original heatsink. Several weeks later a small package from AOpen arrived at the Hutter Labs loading docks. Inspection of the contents revealed an aluminum heatsink and translucent blue plastic fan that bore a strong resemblance to the original 915GMm HSF on steroids.

TECHNICAL DETAILS

This redesigned heatsink seems to be nothing more than a taller version of the original heatsink. It uses a slightly different mounting style for the fan, which may slightly help the fan's airflow but it uses the exact same fan, so any additional cooling power will be coming from the increased surface area of the fins.


New vs. old. At least 4x the cooling surface area.

Curiously, AOpen has rotated the foam spacer on the base by 45°, which has apparently caused interference with the CPU die on several systems.


New vs. old. Why has the spacer been rotated 45°?

The new fan is the exact same 50mm x 10mm fan as supplied with the original Lilliputian heatsink. At 12V it spins at 3400 rpm, but its sonic signature is surprisingly benign. As decent as it sounds, hopefully the increased cooling ability of the new heatsink will let us undervolt this fan to see how much better it sounds when it's running slower than stock.


New vs. old.

Well, enough with the boring technical details, let's see if this thing can turn a sow's ear into a silk purse.

THERMAL AND SONIC TESTING:

All thermal testing was done using the exact same setup and conditions as in the original 915GMm review. The original eensy-beensy heatsink was also re-tested for reference.

Happily, there's not a lot to write about here. The new heatsink performed much, much better than the original heatsink. As unprepossessing as it looks, it even had enough headroom to run the fan undervolted down to an inaudible 5V, as long as the CPU was undervolted to 1.100V. Cooling performance at 7V was darn good, and the fan was just barely audible from 2-3 feet away. And like the fan on the original heatsink, its sonic signature was more like that of a quiet 80mm fan (think Panaflo 80L) than a tiny little 50mm fan.

Temperatures with New Heatsink / Fan
CPUBurn
Load Temp.
°C rise
°C/W
(TDP)
°C/W
(MP)
Fan @ 12V, default Vcore
61°C
40°C
1.90
1.54
Fan @ 12V, 1.100V
49°C
28°C
1.94
1.56
Fan @ 7V, 1.100V
55°C
34°C
2.36
1.90
Fan @ 5V, 1.100V
62°C
41°C
2.85
2.30
°C rise refers to the rise in temperature over the ambient at load.
For default Vcore (1.324V) °C/W - TDP calculations: Intel's TDP of 21W was used.
°C/W - MP calculations: CPUHeat & CPUMSR Projects' estimate of 26.8W was used.

For 1.100V °C/W - TDP calculations: a TDP calculated value of 14.4W was used.
°C/W - MP calculations: A calculated MP value of 17.9W was used.

CONCLUSION

The original review called the 915GMm a "great board, except for the silly heatsink..." This new heatsink removes any concerns I had about this board. It provides enough cooling to run the stock fan at nearly inaudible settings, as long as the CPU is undervolted a bit. My Pentium M sample runs stable at 1.100V, and every Pentium M that I've heard of will run stable between 1.1 to 1.2V so quiet cooling should no longer be an issue for this board.

So, SPCR is in possession of a working heatsink for this board, what about everyone else? AOpen tells me that all the newer 915GMm boards have started shipping with the improved heatsink, and owners that are saddled with the original heatsink can contact AOpen for a replacement. How can you beat that?

Thanks to AOpen for the revised heatsink.

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Discuss this article in the SPCR forums.



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