Too Busy For Words - the PaulWay Blog

Sun 2nd Apr, 2006

The Heatsink Fandango - or how to take two working computers and get only one

40mm heatsink fans are the bane of my existence. No 40mm fan that I've ever owned has kept on spinning silently doing its job until the motherboard has been retired. Instead, I seem to have to replace them every six months or so, as one after another starts whirring, chugging or just plain stopping. And, since each one seems to have a slightly different way of mounting, I end up with carcinogenic heatsink goo all over the place as I attempt to get a good bond that will transfer heat reliably from chip to heatsink.

I've been going increasingly for the Zalman NB47J Northbridge cooler. I have two systems that I've converted from noisy heatsink fan to silent Zalman blue coolness. Unfortunately my Via Epia M-10000's main C3 processor didn't like it - it would run fine but under heavy load such as distributed.net it would reset. At least the board has thermal protection. When my media machine's heatsink fan died, I knew what I had to do - move the Zalman to media and get a new heatsink with fan for the Via.

I'd bought a rather dodgy but suitably beefy Northbridge cooler plus fan from a computer swap meet as a replacement for the Via's Zalman. You know it's a bad sign when the heatsink is a nice glossy black - not matte black anodised aluminium, but something that's been dipped in paint. OK, maybe reflective surfaces radiate slightly more heat than matte surfaces, I don't know. (Cue half-hour distraction reading pages about what's wrong with the US Army, starting from bad camouflage in deserts through to sleep deprivation, out of date equipment and most of their time spent mowing lawns rather than doing exercises.) But it didn't inspire me with confidence.

My interest took a nosedive when I looked at the mounting system for it. The Zalman, in order to accomodate different locations for the Springy Push-In-And- Lock Things that all Northbridge heatsinks seem to have, has a set of arms that have a hex nut that fits into a channel in the heatsink. You get them into roughly the right position, screw them up until their stiff but movable, position them exactly without pushing them through, do up the screw until it's tight, and your arms are locked in position. Good grip, good pull on the arms from the SPIALT, no problems.

The same channel was in the heatsink, but the arms just have a pushed-out lug to keep them in the channel. The springs are supposed to exert enough pressure to push the arms up (at nearly 10° angle) and hold the heatsink down on the chipset hard enough to get a good thermal contact. Yeah, right!.

Sure enough, I tried several times to get it working but it steadfastly refused to be a heatsink for more than about five seconds at a time. Fedora Core 4 would boot up and often not get past loading the vmlinuz file before the machine would happily reset. In one test it was sitting at 40°C in the BIOS PC Health screen, which is far too hot for any chip to be idling at in a Canberra autumn. And each of these tests is carried out by laboriously fitting the board back into its case, plugging everything back in, and going to the other end of the house to plug it back into its KVM port and power, only to have it do a good impression of the Eiffel Tower upside down.

I tried other combinations with other heatsinks, including the one the board originally came with. I tried small and large amount of thermal paste. I tried no fans, low speed fans, high speed fans. It was obviously a cooling problem, since the more heatsink compound I applied, and the presence of a fan, kept it up for a few more seconds. But nothing has restored to it the stability of the Zalman, and the Zalman is now needed in the Media machine.

There are two options left. One is to swap the Zalman back; the last heatsink on the Northbridge of the Media machine was a dodgy piece of flat aluminium with folded sides stuck on with about a five-cent-piece's area worth of heatsink compound, so it can obviously cope with worse heatsink bedding than the Via. But that would leave the glossy black thing with the abysmal fastening mechanism on the Media machine, and I can cope with Dumont being down far better than I (and Kate) can cope with no TV being recorded.

The other is to whip out the final resort: a two-part thermal epoxy resin from Arctic Silver. This should guarantee a good contact with the chip, but at the cost of never, ever being able to take the heatsink off again. So if it turns out that I haven't done quite a good enough job of sticking the heatsink onto the chip, I can't just have another go. It'll be a trip to AusPC Market to buy $300 worth of new motherboard. $300 that I was trying to put into the home loan to be a good boy.

So, here goes. Clean motherboard and heatsink thoroughly, add part A to part B in equal measure, apply carefully to heatsink, stick together and hope...

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