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

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So, how well will this board work as the centerpiece of a super quiet desktop or HTPC setup? The high idle and load temps that were noted during stability testing weren't too comforting, but now it was time to lean on this board, and possibly do a bit of tweaking to optimize things.

First up, we'll test the stock HSF at it's default speed of 12V. After various experiments with the stock heatsink during initial testing, it ended up being installed in it's out-of-the-box configuration using Arctic Silver's Ceramique, which was "burned in" for a full 24 hours prior to thermal testing. I wanted to give the heatsink every chance in the world to perform it's best.

The heatsink comes stock with a 40mm x 10mm transparent blue fan screwed to the top of the aluminum fins. I was told by sources at AOpen that this fan was chosen for its quiet sonic signature, and not for performance. Testing showed that to be easy to believe, as it was pretty quiet for a 40mm fan, especially at 12V. It's probably the quietest 40mm fan I've ever heard, with only a very slight motor hum and a quiet, and rather low pitched whine. It actually sounded more like an 80mm fan than a typical 40mm fan. This low noise comes at the expense of airflow though. There's certainly not much, and the lack of airflow combined with the very small size of the heatsink adds up to a very hot running 20W CPU!

CPUBurn led to full load temps of 79°C in the stock 12V configuration, a situation that didn't bode well for further experiments with undervolting the stock fan. Undervolting the CPU from the default 1.324V down to 1.10V helped somewhat, but I'm not sure that the average user would want to do what it takes to find a stable, lower voltage setting to operate at. Just for fun, I briefly tried it at 7V, with the CPU at default Vcore, but shut it down after it reached the mid 80°C range within less than 15 seconds of firing up CPUBurn. I fully realize that modern CPUs can probably run around 70°C without lots of long-term effects, but I'm not willing to risk my expensive processor in the name of science, so I kind of put the brakes on things and went to "plan B". Here's the temperatures with the stock heatsink:

Temperatures with Stock Heatsink and Fan

Load Temp.

°C rise
°C/W (TDP)
°C/W (MP)
Fan @ 12V, default Vcore
Fan @ 12V, 1.100V
Fan @ 7V, default Vcore
too much
°C rise refers to the rise in temperature over the ambient at load.
°C/W - TDP calculations: Intel's TDP of 21W was used.
°C/W - MP calculations: CPUHeat & CPUMSR Projects' estimate of 26.8W was used.

In this case, "Plan B" consisted of looking for alternatives to the either the fan or the heatsink, or both. The quietest 40mm fans I have on hand are louder than the AOpen fan, so that idea was out. I measured the mounting hole pattern on the motherboard so that I could look for a replacement heatsink that would hopefully bolt right on with a minimum of hassle. I was thinking that perhaps a northbridge heatsink, or perhaps a 60mm type of heatsink would work. Twas not to be, as the hole pattern measured 52mm x 52mm square, a non-standard size for any heatsink I could find. I even tried using a Thermalright NB-1C, the slick little all-copper NB heatsink with all the adjustable mounting methods. It wasn't even close to being able to fit.

Next on my list: heatsinks for embedded motherboards. A fair amount of Googling yielded some promising results, among them some nifty looking all-copper sinks from Coolermaster, of all people. The same Google search also yeilded the fact that AOpen happened to have an online support forum, whose motherboard section was full of people having the exact same heat issues with their 915GMm's and the stock heatsink. One of the posters had just ordered the Coolermaster embedded heatsinks, so I waited and let him be the guinea pig on that one. Well, his heatsink arrived, an it didn't fit the AOpen hole pattern. Apparently AOpen created a hole pattern that was entirely unique to them. Great for selling their own heatsinks, but a complete pain for anyone trying to upgrade to a better heatsink.

Never one to throw in the towel prematurely, and having a Nexus modded Zalman 7000AlCu sitting unused on the test bench, I started measuring things to see if it might be a candidate for the stock heatsink's replacement. The Zalman/Nexus performed superbly on my earlier Pentium M board, even when run completely passive so I figured it might be the ticket for this board as well. When I measured the mounting hole pattern on the Zalman, it came real close to matching the hole pattern on the AOpen 915 board, if it was mounted diagonally across the socket. When I mocked up the Zalman, I found that it would need some minor grinding of it's fins in about three places to clear the various obstacles on the board. I would also need to to make a set of risers approximately 0.560" high to mate the Zalman to the correct height need to work with the Socket 479 and the heatspreaderless Pentium M processor. All this was starting to seem like a bit too much work to fall under the guise of a "minor mod" so I decided not to pursue the time, expense and Zalman grindage that would be required, and went to "plan C".

Plan C consisted of carefully positioning the Zalman/Nexus heatsink on top of the CPU die without any sort of retention mechanism, other than gravity and the stickyness of the Ceramique. Obviously, this would never be something to consider for normal use, but by now I was getting desperate to try something other than the stock heatsink on this board. After carefully placing the Zalman 7000 onto the CPU die, I plugged the heatsink fan + Zalman Fanmate (set to 5V) into the motherboard fan header and fired it up, while keeping my finger firmly planted on the PSU power switch. As it turned out my fears were unfounded as booting into the BIOS showed the CPU running at a chilly 30°C, just about 15°C cooler than with the stock HSF, and almost exactly the same temperatures I was getting with the same CPU on the earlier AOpen 855G board. Booting into Windows got me idle temps of 26°C, and CPUBurn load temps of 46°C, all this with the 92mm Nexus fan in the Zalman 7000 running at an inaudible 5V. Now this is more like it! But unfortunately, the machinations required to properly and safely mount this heatsink on this board are way beyond the average enthusiast.

Zalman 7000AlCu (modded), default Vcore (1.324V)*

Load Temp.

°C rise

°C/W (TDP)

°C/W (MP)

Zalman 7000/92mm Nexus @ 5V
*heatsink not bolted onto CPU, only perched precariously on top.

So where does this leave us? Maybe "plan D" which would involve the stock heatsink with a decent fan mounted above it on a Zalman FB123 bracket? I doubt that would work very well, as the heatsink itself seems to be too ineffective to do its job sufficiently. How about "plan E", having a machine shop drill the 52mm hole pattern into the base of something like the old (but very effective) Alpha PAL6035? Maybe, but it still sounds like too much work to me.

I could go on brainstorming forever, but I'm not going to. If this is the heatsink AOpen wants to use on this board, fine, so be it.


AOpen is one of the very few companies that embraced the Pentium M for the desktop, with two Pentium M boards released over the past six months, and a third, full ATX board that should be available soon. The first Aopen Pentium M board was based on the older, less full-featured, but stable and proven 855GM chipset. This second release is very modern, and full featured. That, plus the m-ATX form factor seems like it would make the perfect solution for an Intel-based quiet HTPC/multimedia system... and it almost is.

"Almost" because of a potentially fatal flaw in an otherwise very nice board. The deficient heatsink: I'm no engineer, but heatsinks can now do a great job of cooling a 100+ watt processor. It's beyond me how someone can design a heatsink incapable of keeping a 20W processor cool. Yes, Intel and others that claim to know this stuff will throw around statements like "70°C is a perfectly safe temperature for the CPU", and "if it doesn't crash, it's stable", but the sort of person (including most SPCR readers) that would be putting a system together using this board probably would be bothered by such temperatures. And if it's not bad enough that the heatsink is sub-par, there's no way to replace it with any aftermarket heatsink because of the oddball form factor.

So where does that leave this motherboard? Fatally flawed might be a bit too strong. It's actually a great board except for the silly heatsink mounting option. I suppose if you could choose to ignore the high CPU temperature, or never tax the CPU with a heavy load, it might be perfectly usable. In fact, the little 40mm fan isn't too bad, is nearly inaudible across the room, and its tone isn't too obnoxious even from as close as a few feet away. That may be fine for some folks, but not for me. I'll pass on this one unless AOpen, or some third-party vendor comes up with a decent heatsink for it.


* Four different video outputs
* Very stable
* 533MHz FSB support
* DDR2 support
* 2 SATA ports and 2 SATAII ports
* A plethora of USB 2.0 and Firewire ports
* HD Audio onboard

* Non-standard heatsink mounting
* Heatsink can't keep CPU cool under load
* No PS/2 ports
* Proprietary FDD port

Much thanks to AOpen for the opportunity to review this motherboard.

* * *

Discuss this this article in the SPCR Forums.


In response to overwhelming criticism from reviewers and users, AOpen has introduced an improved heatsink/fan for its i915GMm-HFS board. It is now standard on all shipping boards. The best news: Owners saddled with the original heatsink can contact AOpen for a replacement. See RH's review of the replacement HSF on the next page.

Mike Chin

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