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#1
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Opteron Overclocking?
Has anyone tried to overclock an Opteron based systems?
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#2
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Adrian Richards wrote:
Has anyone tried to overclock an Opteron based systems? Yes. (not personally, can;t remember where) They scale well 'cos the memory controller is onboard. Ben -- I'm not just a number. To many, I'm known as a String... |
#3
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"Adrian Richards" wrote in message ... Has anyone tried to overclock an Opteron based systems? Is it really worth melting something as new / expensive as an opteron? too expensive as yet to be worth overclocking |
#4
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HamMan wrote:
"Adrian Richards" wrote in message ... Has anyone tried to overclock an Opteron based systems? Is it really worth melting something as new / expensive as an opteron? too expensive as yet to be worth overclocking As far as I know, they run pretty cool thanks to SOI, a heatspreader, relatively low clock and only 1.55V. I reckon you could pump a whole load of voltage in there and not damage it. Maximum rated thermal dissipation is 80W, but since AMD plan not to revise this figure to make upgrading easier (no new HSF required) it's probably considerably lower than that right now. Ben -- I'm not just a number. To many, I'm known as a String... |
#5
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"Ben Pope" writes:
As far as I know, they run pretty cool thanks to SOI, a heatspreader, relatively low clock and only 1.55V. How is it any thanks to a heat spreader? A64 is like an AXP with an extra layer of aluminum and TIM between the chip and the HSF. And AMD chooses the type and thickness of one of the two TIM layers (making TIM reviews even less useful). These would tend to make the CPU run hotter than it would otherwise. CPU heat spreaders should be called "CPU protectors", because they're there mostly to protect the edge of the chip from being chipped by the HSF and probably to discourage people from messing with bridges. |
#6
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Gary W. Swearingen wrote:
"Ben Pope" writes: As far as I know, they run pretty cool thanks to SOI, a heatspreader, relatively low clock and only 1.55V. How is it any thanks to a heat spreader? Getting the thermal interface good is less important as you have much more area. A64 is like an AXP with an extra layer of aluminum and TIM between the chip and the HSF. And AMD chooses the type and thickness of one of the two TIM layers (making TIM reviews even less useful). These would tend to make the CPU run hotter than it would otherwise. It's not that much like an XP is it really? CPU heat spreaders should be called "CPU protectors", because they're there mostly to protect the edge of the chip from being chipped by the HSF and probably to discourage people from messing with bridges. Agreed that they protect the chip. As to whether they were put there to discourage people from playing with bridges is probably debateable. I don't think it was any accident that XPs are so easy to overclock. Ben -- I'm not just a number. To many, I'm known as a String... |
#7
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"Ben Pope" writes:
Gary W. Swearingen wrote: How is it any thanks to a heat spreader? Getting the thermal interface good is less important as you have much more area. Getting it good is just as important (more, I think) because of the added thermal resistance of the extra layer of TIM and package lid. You're hoping that AMD gets the chip-to-lid thermal interface good on the small chip surface and your lid-to-heatsink thermal interface job is made more difficult because you now have more area to cover with a good layer of TIM. The lid doesn't do much heat spreading anyway because the heat sink does it so much better than the thin lid. A64 is like an AXP with an extra layer of aluminum and TIM between the chip and the HSF. .... It's not that much like an XP is it really? Like I said, it's like an XP with an extra layer of TIM and the lid/spreader. It's almost twice as big in area as the XP which probably helps spread the head some, but that's a different issue; it would still be better to put the heatsink on the "bare" chip. (From some thermal plots I've seen, small parts of the chip can be much hotter than others, leading me to believe that the chip considerably less heat-conductive than aluminum or copper, but I don't really know.) |
#8
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Gary W. Swearingen wrote:
"Ben Pope" writes: Gary W. Swearingen wrote: How is it any thanks to a heat spreader? Getting the thermal interface good is less important as you have much more area. Getting it good is just as important (more, I think) because of the added thermal resistance of the extra layer of TIM and package lid. You're hoping that AMD gets the chip-to-lid thermal interface good on the small chip surface and your lid-to-heatsink thermal interface job is made more difficult because you now have more area to cover with a good layer of TIM. Oh come on... twice the area gives you twice the ability to transfer heat. Which means that pe sq mm you don't need as good a thermal interface to dissipate the same energy. The lid doesn't do much heat spreading anyway because the heat sink does it so much better than the thin lid. So only the middle bit of the lid heats up? I doubt it. A64 is like an AXP with an extra layer of aluminum and TIM between the chip and the HSF. ... It's not that much like an XP is it really? Like I said, it's like an XP with an extra layer of TIM and the lid/spreader. So it's like an XP... It's almost twice as big in area as the XP which But twice as big, and uses SOI which drsatically reduces the capacitance of the transistors in the chip, reducing power requirements and heat production. So when we're talking about the thermal characteristics, it's not that similar, is it? probably helps spread the head some So now area is important in transferring heat? but that's a different issue; it would still be better to put the heatsink on the "bare" chip. Only if you do a better job of the thermal interface than AMD. OK, I concede. Maybe the heat spreader doesn't always allow an increased thermal dissipation from the chip. Without hard evidence, neither of us know for sure. Ben -- I'm not just a number. To many, I'm known as a String... |
#9
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"Ben Pope" writes:
Gary W. Swearingen wrote: "Ben Pope" writes: Gary W. Swearingen wrote: How is it any thanks to a heat spreader? Getting the thermal interface good is less important as you have much more area. Getting it good is just as important (more, I think) because of the added thermal resistance of the extra layer of TIM and package lid. You're hoping that AMD gets the chip-to-lid thermal interface good on the small chip surface and your lid-to-heatsink thermal interface job is made more difficult because you now have more area to cover with a good layer of TIM. Oh come on... twice the area gives you twice the ability to transfer heat. Which means that pe sq mm you don't need as good a thermal interface to dissipate the same energy. When you said "more area", I thought you were talking about the top of the lid (the "heat spreader"), since I was discussing your comment on those. Now you're talking about "twice the area" which leads me to think that you're thinking about the chip (die) area. I agree with the gist of your statement above on that subject. (But I can quibble with that too: 1) You're going to dissipate the same energy, no matter how good or bad your thermal interface is; the important issue is how hot your chip (actually, the hot spots of the chip) are going to be. 2) If 95% of the heat is coming from a small portion of the chip where most of the calculations are occuring, then it barely matters how big the chip is. That's an exageration, of course, but you should get the point. Most of the heat from such hot spots flows up through the thin chip, the TIM, any lid and extra layer of TIM, and into the heat sink, and much less first flows sideways through the chip and/or the lid.) Yes, of course a much bigger chip producing about the same heat can be said to run cooler; you won't (and haven't) gotten any argument from me on that. But the question was whether a lid helps it run cooler. Now, I must admit that a lid CAN help a CPU run cooler in some circumstances that shouldn't matter to overclockers: Like with no heat sink or with a VERY crummy one or maybe even with a copper or silver lid with a cheap (thin) aluminum heat sink. The copper "cores" of some aluminum heat sinks is a kind of heat spreader, but you'll notice that they tend to be much thicker than CPU lids (though that might just be eye candy). But AMD lids look like aluminum and overclockers use good heatsinks, often with copper bottoms, at least. (It would be interesting to know the thermal resistance of the copper-aluminum interface in Cu-Al heat sinks.) But someone desiring the coolest possible chip would not use an extra TIM layer, if he had control over the complete design and didn't have to use a very cheap heat sink or worry about chip chrushing. The lid doesn't do much heat spreading anyway because the heat sink does it so much better than the thin lid. So only the middle bit of the lid heats up? I doubt it. And I didn't say or even imply that. I implied that the bulk of the heat flows into the heat sink without flowing through the parts of the lid that don't touch the lid. Some of the heat does, of course; how much depends on the thickness of the lid. There are two ways to look at this that should help you see my point. With both, assume that the lid and heat sink are made of the same material and that we're only discussing one type of CPU chip. 1) Consider lidded and unlidded CPUs with heat sinks. If some imaginary TIM that had the same thermal resistance as the lid and sink was used between the lid and sink, then there would be little or no difference between a lidded and unlidded CPU; the thermal resistances are nearly the same for both. It's as if the lid was the bottom of the heat sink. But now replace the imaginary TIM with real TIM and you should see that you've made the situation worse. It would be better to not have to use that layer of TIM, as with the unlidded CPU. 2) Think of an unlidded CPU with a mounted heat sink. Now imagine that you cut the heat sink a bit above the CPU chip and use the resulting slab as the lid of a lidded CPU. You'll need to add another layer of TIM between the lid and sink, and the result can only be worse than if you had stuck with the unlidded CPU. BTW, while the non-middle bits of the lid do heat up, they don't heat up as much as the middle bits. Again, think of the lid as just a lousy bottom of your heat sink. Even if it was a good bottom of a heat sink, the parts of the sink (and lid) away from the chip are cooler than those near it; that should be fairly obvious. Think of the heat flowing out of the chip surface up through the TIM/lid/TIM/sink in a nearly hemispherical pattern. The lid design effectively slices a layer off the bottom of the sink and then puts it back on with TIM, with several bad side effects: The chip TIM is chosen by AMD instead of you, and it can't be replaced when degraded through a combination of overclocking and time. The thin layer is possibly changed from copper to aluminum. An extra layer of TIM is introduced. The extra layer has a large area which makes it harder to get a thin even application of TIM and makes it essentially impossible to apply the same amount of pressure to both layers of TIM (so the outer layer is not as well pressed as one would desire, without putting too much pressure on the chip, despite the lid) (unless the CPU lid is strong enough to avoid transferring much force to the chip, which I doubt). A64 is like an AXP with an extra layer of aluminum and TIM between the chip and the HSF. ... It's not that much like an XP is it really? Like I said, it's like an XP with an extra layer of TIM and the lid/spreader. So it's like an XP... Yes, it is. They both run hotter than they could without a "heat spreader". You must not be used to this common English figure of speech (called a "simile") in which two essentially unlike things are compared in some "like" characteristic(s). It's done all the time, like in "John is like Einstein with no cerebrum." Is John like Einstein? Yes (and no). I hope that helps. It's almost twice as big in area as the XP which But twice as big, and uses SOI which drsatically reduces the capacitance of the transistors in the chip, reducing power requirements and heat production. Yeh, yeh. And many more transistors, both in the caches and in the high-temp computing parts of the chip which have more bits. But none of this has anything to do with the issue of "heat spreaders". So when we're talking about the thermal characteristics, it's not that similar, is it? But I wasn't talking about thermal characateristics; I was talking about whether heat spreaders help CPUs run cooler. Like I said in the same sentence, the size of the chip is a different issue. In this discussion, I consider the AXP and A64 thermal characteristics to be effectively identical to each other and to any other heat-producing chip. probably helps spread the head some So now area is important in transferring heat? I didn't say anything there about transferring heat; I was referring to the fact that the sources of heat are more spread out on the A64. (The max heat generation of the two CPUs are not much different.) but that's a different issue; it would still be better to put the heatsink on the "bare" chip. Only if you do a better job of the thermal interface than AMD. Nope. Both me and AMD can do good jobs with our two interfaces and still wind up with a hotter-running chip than yours with a single poor interface (unless it's TOO poor, of course). OK, I concede. Maybe the heat spreader doesn't always allow an increased thermal dissipation from the chip. Without hard evidence, neither of us know for sure. Without hard evidence or convincing analysis, both of us will have to rely on our own analysis or on the handwaving of AMD's and Intel's marketing people. Pick one. |
#10
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