Replace Northbridge Thermal Compound
When you free the two spring clips that hold the EX475’s northbridge heatsink in place, you’ll see the pad of pink adhesive that looks and feels very much like chewing gum that HP used for heat transfer from the SiS northbridge to the aluminum heatsink. On my system, the default northbridge temps ranged from 57 degrees to 60 degrees Celsius. After I replaced the HP chewing gum adhesive with Arctic Alumina, adhesive temperatures stayed more or less the same, so I opted for Arctic Silver instead. At that point, temperatures dropped 2 degrees Celsius right away and temps have been trending slowly downward as the Arctic Silver compound cures and sets up better heat transfer. I’m currently reading measurements of 54 degrees Celsius from the northbridge and expect it may go as low as 52 degrees Celsius by the time the compound cures completely.
To clean the old thermal adhesive from the chip and the heatsink, you’ll need a solvent of some kind. I tried both 90% Isopropyl alcohol and some of my wife’s acetone nail polish remover. Do yourself a favor and go straight for the acetone, but use a small knife blade to scrape as much of the adhesive off both surfaces that you can first. This will ensure the best results. Also, keep the solvent away from the foam pad at the edge of the heatsink, which will dissolve the adhesive used to secure the foam padding much more easily than the thermal adhesive you’re trying to remove.
After you’ve cleaned off all the pink goop, deposit a small dab of Arctic Silver in the middle of the northbridge chip. I used an old credit card to smooth it into a thin layer that covered the whole chip surface, but you can also use a knife blade or a business card to do likewise. When you reattach the heatsink, you might want to put something heavy on top of the fins for five to 10 minutes afterward to encourage the compound to bond the two surfaces more tightly. I used a can of beans to do this, and it seemed to work pretty well.
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