I hear that many thermal greases require time to reach optimum efficiency. I have noticed on my current processor that, after 1-2 weeks, the temp under load has dropped from 57C to 53C (FX-55 Clawhammer using Arctic Cooling thermal grease).
So, as temperature can be a controlling factor during OC, would it be better to let the heatsink to bed in and wait for the temps to drop before attempting any OC ?
I have just got an Opteron 170 and Zalman CNP9500 hsf, and am itching to see what it can do.
This will be my first OC project, so apologies if this is a noob question.
arctic cooling website itself says that it is true it takes some cycles to reach optimum efficiency.
as far as overclocking goes, feel free to overclock.. it's just that if you spend lots of time going through every permutation of settings to find your maximum overclock, your time will be wasted because in 2 weeks you'll have more headroom to OC further.
I think I will have to play around with it sometime over the weekend (can't just sit there and wait), so will make notes as to how far I can get, and then try again once the hsf is bedded in and the temps drop.
Unfortunately, I don't have any of the Arctic Cooling thermal paste left, so will use the Thermaltake stuff that came with the XP-120. Looks to be about the same, although can't find the specs anywhere. I'll also check the stuff that Zalman sent me.
Some thermal greases take longer to mate than others, due to the size, composition and quantity of the solids they may contain.
It also depends on the surface finish of your heatsink.
Shin-etsu produces thermal compounds with very low thermal resitance due to their very high aluminium particle content. These compounds are excellent for mass produced heatsinks with inferior surface finishes. On finely finished heatsinks they are detrimental, as the very high particle content will restrict mating of the cooling surface to the heat source. Full burn in for this type of compound can exceed the life expectancy of the processor.
Silver based compounds work very well on semi-flat finishes and are particularly efficient with laminated type heatsinks, where the cooling surface shifts due to thermal expansion between the laminae. On laminate surfaces that are constantly changing, the burn in time is ohhh... roughly infinity.
Pure, high quality silicone grease is most efficient when used with bare dice and mirror polished cooling surfaces. There is no real burn in time for this stuff.
High quality ceramic based compounds work exceptionally well on almost any surface, because the particulate is particularly fine. This stuff can be burned in in about 40 minutes, by running the die at about 60C for half an hour, then allowing it to cool to ambient. The thermal resistance of Arctic Silver Ceramique is at least on par with any other type of compound I've used and on any surface I've used. It is, by far, the most robust and user friendly thermal compound on the market.
A friend of mine who worked for Gruman Aerospace said they did hundreds of tests to find the best finish for heatsinks. He said they found that finishing the sinks with 600 emery cloth worked best, he also said that a mirror finish was as bad a a rough one. He said they tried dozens of different pastes, oils etc. He didn't know which one was the best since they were all in the same type bottles that were numbered so that Brand Names would not effect the outcome. He did say that they all worked best with the 600 finish. Makes you think about all the time & money spent on mirror finishes.