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An Anonymous Coward writes:

http://www.dansdata.com/goop.htm [dansdata.com]

Overclockers love grease.

Thermal grease, to be exact. "Thermal transfer compound", if you want to be formal. It's the stuff you put between your CPU and your CPU cooler, to aid in the transfer of heat from the former to the latter.

All modern PC CPUs produce enough heat that they need a heat sink. Almost all of them need a heat sink with a fan. Many heat sinks come with some sort of thermal transfer thingy pre-applied - a patch of grease, or a square of chewing-gum-like semi-solid material, or just a rubbery pad for the low performance units. Most CPUs don't produce enough heat that the stuff you put between the chip package and the heat sink matters very much, as long as the computer case has decent ventilation and the ambient temperature isn't sauna-like. There just has to be something between CPU and heat sink.

The reason why there has to be something there is that the two mating surfaces of processor and sink aren't flat. They may look flat. They may have a mirror polish. But, on the microscopic scale, they look like a scale model of the Andes. And the mountains on one item do not match the valleys on the other.

Without thermal transfer compound, everywhere heat sink metal doesn't mate with CPU package material is a teeny-tiny air gap. Air is a good thermal insulator. As long as your heat sink looks flat when you lay a ruler on it then there'll be a decent amount of actual contact, of course, but the amount of heat that'll actually make it around the air gaps may be surprisingly small.

Hence, thermal compound. It's grease with lots of minuscule thermally conductive particles mixed into it, basically. It doesn't conduct heat as well as direct contact, but it's a heck of a lot better than air gaps.

A popular view among those of us who've spent more time cleaning thermal grease off our hands than we'd care to remember is that it doesn't really matter much what kind of thermal grease you use. Plain cheap white zinc-oxide grease, fancy silver grease, ultra-fancy super-exotic better-than-the-stuff-NASA-uses grease; they're all much the same. As long as you apply the stuff reasonably sparingly, you'll be fine.

I'd never actually tested this, though. Perhaps the marketing bumf for the current crop of exotic super-greases was right; perhaps they really are spectacularly better than plain cheap white thermal goop. Perhaps the fancy greases have advantages beyond their thermal performance, too.

Since I'd recently received a few new super-goops for review, it was time for a comparison.

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