>On 14/3/09 02:32, "Wallace Adrian D'Alessio" <[email protected]> wrote: > >> Overclockers who are set on defeating heat to preserve costly CPUs >>yet squeeze >> extreme clock counts out of them have been known to polish the CPU and >> heatsink with ever finer grades of wet or dry paper starting with 1000 grit. >> And even going to finer grits of polishing compound. Some may even >>" lap : the >> surfaces together with a polishing compound. >> >> Then they apply the thermal paste after all of that. >> >> In theory the more closely the parts surfaces match and the >>thinner the paste >> needed to >> make up the difference the faster and therefore the more successful the heat >> transfer will be. >> > > Seems strange - the laws of physics would suggest that a coarse finish - >rather than a polished surface - would provide a much greater surface area >for a face to face contact - with the compound filling the pits in the >coarse finish... > >Pete >~------~--~---
With a coarse finish the surfaces are held apart by the metal to metal contact at random spots and the interstices are filed with compound. The compound has a finite, even if small, Thermal resistance. The length of the path through the compound is defined by the roughness of the surfaces. The smoother the surface the smaller the interstices left by the metal to metal contact points. Thus the layer of Compound necessary to fill the interstices is thinner. It could be argued and possibly answered by experiment that there could be a surface condition in the range between a very rough finish and a finish that imposes a Casimir force that would give the minimum thermal resistance at a reasonable cost of Time, Money and Resources. I would imagine that the Engineers at the Heat sink, Thermal Paste, Processor and Computer Manufacturers have thoroughly investigated the situation. If they have followed good engineering practices they have experimented and found a workable solution within the Triple Constraint (Money, Resources, Time). The Over Clockers are the modern equivalent of the old Shade Tree Mechanics squeezing the last possible Horsepower/Torque out of a Flat Head Ford engine; as they work within their version of the Triple Constraint. If it works for them, Hurrah, ErnieG --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed Low End Mac's G3-5 List, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list?hl=en Low End Mac RSS feed at feed://lowendmac.com/feed.xml -~----------~----~----~----~------~----~------~--~---
