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Does CPU voltage matter regardless of core temp?
If you can keep the CPU cool, does it matter how high the voltage gets? Is the potential damage to a CPU from OC'ing solely due to heat or are there other considerations?
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Does CPU voltage matter regardless of core temp?
Doc wrote in
: If you can keep the CPU cool, does it matter how high the voltage gets? Is the potential damage to a CPU from OC'ing solely due to heat or are there other considerations? Every 6 degree Celcius halves the live of a chip. Increased voltage increases disssipation, and educes livetime. BUT... If you have a deep pocket ready to buy new chips, you have no problem. |
#3
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Does CPU voltage matter regardless of core temp?
Doc wrote:
If you can keep the CPU cool, does it matter how high the voltage gets? Is the potential damage to a CPU from OC'ing solely due to heat or are there other considerations? If you look at the datasheets for silicon chips, there is a section called "Absolute Max". Once the voltage gets past a certain point, there are breakdown mechanisms to deal with. http://en.wikipedia.org/wiki/Avalanche_breakdown Processors vary, as to how the Absolute Max, meshes with the range of VID codes. On some processors, it's all too easy to go over a safe value. On Core2 45nm processors, about 1.4V is a safe long term overvoltage. And that was experimentally determined by participants on xtremesystems.org forums. When it came to ruining certain processors, it wasn't the absolute voltage which hurt, but a voltage difference that mattered. On the AMD FX processors a while back, there was a "VCore" voltage, and also a voltage used to feed the memory interface. It turned out, again, after users experimented with it, that if you increased VCore, you were also supposed to increase the memory interface voltage at the same time. It seemed, if there was a large delta between the two, some currents would flow where they should not, inside the processor, ruining it. Normally, a datasheet will state in unequivocal terms, what the max difference can be, such as Absolute Max VCore 1.6V VCore - VDimm 0.6V and that would tell you, if you used 1.6V for the VCore, you should use a bit more than 1.0V for the VDimm. That's in order to keep the delta below the stated value. Chips can be quite complicated when it comes to stating these voltage relationships, and especially when they have as many as five input voltages. In the case of the AMD FX processor family, the dataaheet only addressed VCore, and did not mention there was a delta spec to be met. And again, the experimenters on the enthusiast forums, ruined FX processors until they figured it out. (That dropping VDimm between experiments, with a constant VCore, resulted in a very expensive chip being ruined.) So this is how it works. 1) Processor has hardware limits on the VID code that can be emitted. Normally, that would provide some level of protection against end-user abuse. But there were also chips (like my P4 Northwood), where it's all too easy to set VID to a deadly value (so-called instant death syndrome for that processor). Some processors "wear out" at the higher voltage, rather than dying instantly. A Tualatin processor at the wrong voltage, lasted an average of three weeks before dying from it. (Using a Slot 1 motherboard which lacked the appropriate, lower Tualatin core voltage to run the slocket.) 2) Motherboard manufacturer bypasses this protection and adds "boost" features to give you more voltage. 3) Processor datasheets gives some idea on Absolute Max. 4) Enthusiast experimenters determine what the "real" safe value is, ruining multiple expensive processors to get the value. If you wait long enough, all the necessary information is out there, to be located by your search engine. That's how I could find a value for the limits on my 45nm Core2. Someone else ruined their 45nm Core2, so I could know what that value is. And don't trust my values mentioned above. Do your own data mining. You spent good money for the processor, and the information is out there. Take responsibility for your own experiments! I've never actually abused my 45nm Core2 (it's never been overclocked). I did try it on my 65nm Core2, because those are known to be a bit more tolerant on voltage. It's not worth the trouble on my 45nm one. I just leave that one at nominal (so I can type this message, of course :-) ). Paul |
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