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OK, here we go... ;] Note I said 'seem', due to the fact that through natural convection there will be a more uniformly distributed temperature pattern across the the bottom of the case as opposed to a high-temperature concentration under the processor when there is an established conductive cooling path to the 'heat sink' (desk, stone table, etc.) >If the processor is cooled by conduction to the case, *all* that matters >to the processer is the temperature of the case. If the case is cooler, >it's better...period. True, if the thermal system is one-dimensional. It's not. The conduction equation is also not isotropic (unlike rocks). Your theory about it melting on a stone table because it 'conduct(s) *very* slowly' is also flawed. You are confusing the first-order thermal response with the thermal conductivity. Thermal conductivity determines the rate of heat flux through a material and the thermal mass (density*specific heat) determines the rate at which a unit volume of material will reach a steady-state temperature. Stone (like granite) actually has a rather good thermal conductivity (2-5x better than wood or formica), and a good size table (due to it's long thermal time constant) would actually behave much like an 'infinte heat sink' (constant surface temperature). >One experimentalist is worth ten theorists :). One governing equation is worth ten misinterpreted observations. ;] Regards, -Ted At 07:19 PM 3/9/96 +0100, Victor Kress wrote: >>At 11:13 AM 3/8/96 -0800, you wrote: >>The case may seem cooler when it is up on it's feet, however, the processor >>will be hotter. >> >Now wait a minute. If the processor is cooled by conduction to the case, >*all* that matters to the processer is the temperature of the case. If the >case is cooler, it's better...period. It doesn't matter if the case was >cooled by conduction or convection. As someone who does calculations of >heat flow in rocks, I can tell you that some materials conduct *very* >slowly. For example, one could, in theory, melt the case running a tp on a >stone table with no convection. At least your lap has both a temperature >sensor, and a boiling-point governor :). Go for whatever keeps the case >the coolest. One experimentalist is worth ten theorists :). > >In my experience (using my lap sensor), most of the heat is generated in >the charging battery. If you want to keep the heat load down, the best >strategy would be to remove the battery and run on AC. > >---------------------------- >Victor Kress >Geophysical Laboratory >5251 Broad Branch Road N.W. >Washington, D.C. 20015-1305 >(202) 686-2410 x2489 >web page: http://granite.ciw.edu/~kress >--------------------------- ******************************* Ted Frederick Strategic Programs Manager Worldwide Practice Management Cadence Design Systems, Inc. T:408.894.2275 F:408.894.3484 ******************************* "The idea that information can be stored in a changing world without an overwhelming depreciation of its value... is false." -Norbert Weiner (the father of 'Cybernetics'), 1950