CPU Heat Comparison: How Hot is Prescott?
by Derek Wilson on April 16, 2004 4:32 AM EST- Posted in
- CPUs
Final Words
From our data, it doesn't seem that Prescott is really that much hotter than Northwood. Like we mentioned earlier, though, heat output and our temperature measurements might not scale at the same rate. In other words, since Northwood is cooler than Prescott, our thermistor might be getting cooled even more by the fan. This could mean that Prescott and Northwood are even closer in total heat dissipation than in our temperature measurements. We are always working on ways to better collect this information, but hopefully what we have seen has been helpful.There is, of course, a temperature increase in Prescott though. But where did it come from? Prescott has about three times the number of transistors as Northwood (due to pipeline increases, the addition of 64bit functionality, and (not least) a doubling of the L2 cache). Prescott is fabbed on a 90 nanometer process rather than the 130 nanometer process of Northwood, which means that Prescott will have a higher power density.
There could also be some impact on increased temperature from Intel's new strained silicon technique. This increases the electron mobility through the body of a transistor. What this means is electrons move faster and transistors can switch on and off more quickly (something very good for high speed processors). Of course, this also means that transistors can end up leaking more current through them when they are off. This increases the power used by the chip which in turn increases heat output.
We asked Intel what (if any) effect actually using the 64bit extensions in Prescott would have on temperature, and we were told that it shouldn't have a significant impact on heat. Intel indicated that with the right 64bit application running we might see Prescott draw 2 or 3 more watts of power. Enabling and using the 64bit extensions will use parts of the chip that can currently remain happily disabled. Hopefully Intel will be right when they say that turning on this feature won't impact heat too much. Of course, we'll be there to test it out as soon as we can get ahold of a 64bit enabled chip.
We can't really be sure right now how much each of these factors affect Prescott's temperature, but all of them surely contribute.
The final issue we need to consider is the motherboard issue. Prescott is powered by a lower voltage than Northwood, but consumes more power. This means that it necessarily draws much more current. Though Intel did get the power requirements out to motherboard manufacturers, there may be some issues with Prescott support. Intel maintains that motherboards that were not designed for Prescott won't boot Prescott (and won't hurt either component), there sill may be some unforeseen issues, as even companies designing earlier P4 motherboards with an eye to Prescott wouldn't have had anything to test their motherboards with back when they shipped.
When it comes down to it, there are four options early P4 motherboards and Prescott. 1) Everything could work fine. 2) The system may not overclock very well. 3) The system may run but with reduced stability. 4) The system may not run at all. If there is enough interest, we may end up looking into Prescott and motherboard compatibility. Feel free to let us know if that would be something you would like to see.
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Xentropy - Monday, April 19, 2004 - link
"Most of us here are not mindless zealots who believe everything we read."Unless it's anti-Intel propaganda.
"but i have seen a prescot melt motherboards"
Have you? How many motherboards? Online in some forum or on HardOCP or whatever doesn't count. Personally seen, in person, how many?
Pumpkinierre - Sunday, April 18, 2004 - link
#46 I thought that was standard with Win XP. When I looked at the idle temps., I thought that might be the problem. On my K6-3/Win98, I run Rain which does the same thing. Good Post!lesovers - Sunday, April 18, 2004 - link
The main reason the AMD XP chips are so much hotter at ilde is they do not normally implement the HALT command like the P4s. The VIA KT chipsets (266, 333 and 400) have registers that can enable the CPU to HALT. Link for this is:http://www.ocmodshop.com/default.aspx?a=125%20
My XP2000 cool down be by about 20C at idle with the chipset registers changed !!!!!!
boardsportsrule - Saturday, April 17, 2004 - link
ok wow, how can you have a 3.2 prescot be at 34C with a medeocer heatsink, when i see people complain about high temps with their 2.8 prescott using a sp-94...then onto how could a 2600+ be hotter then a 3.2 prescott...i havent seen a 2600+ melt a motherboard, but i have seen a prescot melt motherboards... this stinks of intel...wounder howmuch they are paying him?ZobarStyl - Saturday, April 17, 2004 - link
This processor is supposed to carry Intel through something like 4.0+ GHz when Tejas gets here; if it's this hot against a Northwood, how do they expect to hit past 3.8 or so without watercooling or Prometia's built into standard desktops. The question isn't whether or not Prescott is a bad processor (it's not a disaster of Williamette proportions) but whether or not it can carry the weight Intel is slated to heft onto it's back for the next cycle.mindless1 - Saturday, April 17, 2004 - link
Margalus, get a grip!Even INTEL specs it to run that much hotter. Will you not even believe Intel?
mechBgon - Saturday, April 17, 2004 - link
Margalus, I've seen several Forum members try the Prescott and go back to their Northwoods because the Prescott was running very, very hot and/or doing scary stuff to their motherboards. And these are neither AMD zealots nor newbies. IIRC one of them is running a Prometia phase-change cooling system and another is running watercooling.Margalus - Saturday, April 17, 2004 - link
I can't believe the number of amd fanatics that just can't accept reality. the prescott is not as hot as the anti intel fanatics are saying. This article was pretty well done for the comparisons they did. All of you saying how it is bs have never even used a prescott, you just listen to clueless people like cramitpal who haven't even passed 3rd grade yetAIWGuru - Saturday, April 17, 2004 - link
"Of course, we'll be there to test it out as soon as we can get ahold of a 64bit enabled chip."Why are you waiting for a 64 bit prescott? Why not use the A64 you already have?
AIWGuru - Saturday, April 17, 2004 - link
Coruscant, your understanding is incorrect.What you're TRYING to describe is the flow of (thermal) energy to the path with the least resistance - the movement of hot to cold.
What you forgot to take into account is that once the heatsink starts to "absorb" heat it may quickly cease to become the path of least resistance.
Regardless, this test is fundamentally USELESS as, unless the dissipation rate of the heatsink has been exceeded, any measurement will be the same.
Because heat does not build up on a linear scale, any measurement above that level will also be innacruate.
The placement of the probe is also somewhat stupid.