Author: Aaron Gordon
Date: 14:07:33 03/18/03
Go up one level in this thread
On March 18, 2003 at 16:46:10, Robert Hyatt wrote: >On March 18, 2003 at 15:45:44, Aaron Gordon wrote: > >>On March 18, 2003 at 10:32:07, Robert Hyatt wrote: >> >>>On March 18, 2003 at 00:38:31, Aaron Gordon wrote: >>> >>>>On March 18, 2003 at 00:06:36, Robert Hyatt wrote: >>>> >>>>>On March 17, 2003 at 22:37:33, Aaron Gordon wrote: >>>>> >>>>>>On March 17, 2003 at 15:26:15, Sakkas Takis wrote: >>>>>> >>>>>>>The AMD are geting very hot when you use chessprograms >>>>>>>Go for Intel >>>>>> >>>>>>How do you figure? Look at both AMD and Intel technical documents (or test one >>>>>>yourself). AMD's run quite a bit cooler (by some 20-30 watts). >>>>> >>>>> >>>>>Just for the record, "watts dissipated" is not the same thing as "running hot or >>>>>cool." The Cray-3 for example radiates 125 kilowatts. Yes, that is kilowatts. >>>>>It runs about -70C or so, immersed in liquid. A chip can convert more watts to >>>>>heat, but _still_ run cooler if it has a solid path for the heat to escape >>>>>quickly (as does the Cray with copper rods and plates everywhere). >>>>> >>>>>That is the limiting factor on speed, in fact. Ramp up the voltage to ramp up >>>>>the clock and eventually you reach the point where the heat can't get out as >>>>>quickly as it builds up, and the thing melts. >>>> >>>>If you have the exact same cooler (lets say 0.15 c/w) with the exact same >>>>thermal compound (Arctic silver 3 for example) then more watts means more heat. >>>> >>> >>>Let's define heat. >>> >>>1. Energy produced by current leaking to ground thru resistive elements. >>> >>>2. Energy that can not escape the CPU core due to lack of a good heat- >>>transmission pathway. >>> >>>1. Is not a problem, so long as 2 is not a problem as well. IE I can, in a >>>single chip, radiate 125 kilowatts, so long as I can also conduct 125 kilowatts >>>of heat _out_ to something that can absorb it. >>> >>>The cooler is only part of the equation. You have to conduct the heat away from >>>where it is produced and get it to a place where the cooler can conduct it to >>>whatever medium it uses to dissipate the heat into the atmosphere. >>> >>> >>> >>> >>>>I'm going to round down the P4 to 100 watts (I think it's closer to 110 watts). >>>>Anyway. A cooler with a 0.15 c/w rating and a 27c ambient temperature would keep >>>>the P4 at 42C. Now, lets try that with an AthlonXP 2800+ (rounding to 75 watts). >>>>39C cpu temp. >>> >>> >>>Again, that is only _part_ of the equation. Your "cooler" can only dissipate >>>that heat that gets efficiently conducted to the surface of the chip. If one >>>chip conducts heat better than the other, that chip is going to run cooler, >>>until it runs up against the limit of the cooling device. If one chip conducts >>>worse than another, the cooler will _not_ dissipate its rated heat, because the >>>chip can't get the heat to where the cooler can pick it up. >>> >>> >>> >>> >>>> >>>>As long as the cooling remains the same P4's are going to run hotter. No doubt >>>>about that. More watts means more heat. Doesn't matter if you're putting a >>>>cooling block on the core thats room temp or absolute zero. Heat is heat. >>>>1 watt > 2 watts. >>> >>>So? If a processor only produces 1 watt of heat, it can run hotter than a >>>processor that produces 2 watts, if the 1-watt processor can't transfer the >>>heat to a point where it can be removed effectively. >>> >>> >>> >>>> >>>>Lets try a 'normal' heatsink/fan c/w rating. Say, 0.35c/w. 27C ambient, 100 watt >>>>cpu, thats 62C full load. Pretty toasty. >>> >>> >>> >>>Again, that is ignoring heat conduction. You have to deliver the heat to >>>the cooler before the cooler can remove it. >>> >>> >>> >>> >>> >>>>Just for the fun of it lets throw in my particular setup. AthlonXP 2512MHz, >>>>1.98v, 137.849 watts. If you think THAT is hot.. you should see my friends 200 >>>>watt P4 @ 4GHz. Anyway, 15C ambient air temp on average, 16C water temp, liquid >>>>cooler c/w is 0.0766c/w and the cpu temp is 26.56C full load. :) >>> >>> >>>Same comment. Cooler capacity is only _part_ of the equation. If the heat >>>can't travel to the surface of the chip, no cooler in the world is going to >>>help. >>> >>>I mentioned the cray-3 earlier. Chips have no "carriers" at all to increase >>>density. Chips do have small gaps between them for the connections to be >>>robot-welded. And for liquid to circulate right on the chip itself to extract >>>the heat. >> >>I guess you've never seen a Pentium 4 cpu & AthlonXP cpu up close. The AthlonXP >>would conduct heat better through to the heatsink because the core itself is >>extremely close to the top of the metal at the top. Pentium 4's have an >>aluminium heat spreader covering their core so the heat transfer is impared >>quite a bit, add that on top of a core that puts out more watts and you've got >>trouble. I figured you already knew this, though. > > >I've not seen 'em both up close. Whether the aluminum is bad or not is not a >question I would >answer myself. The Intel folks are good enough and it might be that was good >enough to >dissipate what they had to deal with. As opposed to using say Copper. (or >silver, heaven >forbid). > >But even _that_ is not all of the equation. The heat is produced in the various >junctions in >the chip itself. Getting the heat from there to the dissipator (whether that be >a sink, a cooler, >a Peltier device or whatever is not the point here) is an interesting >engineering problem in >its own right. > >There is as much materials engineering going on in a chip design as in the >electrical engineering >side. Yes, Silver would be best no doubt. Would increase chip prices by quite a bit I think. Copper would be all around the best bet IMHO. What you state is true indeed, but it doesn't change the fact that a P4 runs hotter than an AthlonXP. :) I've worked with both types of chips first hand. The P4 gets way, way too hot. It reminds me of the old cyrix chips. Slow, runs very hot, etc.
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