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Fluctuating processor core voltage

Last response: in Components
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March 5, 2012 1:39:06 PM

I am not new to using PCs, but I am fairly new at building them. I have only recently noticed a fluctuating processor core voltage on one of my systems, which tends to stay at the low side, around 0.88-0.89, but every few seconds jumps to 0.90, 0.92, 1.00, and sometimes even 1.2x for a second or two. Memory voltage is on the high side, 1.58, but it is stable. +3.3v is also mostly stable but on the high side, 3.44-3.45. All voltages are read with Intel's Desktop Utilities. This system is very lightly loaded and does not even have a graphics card. None of the components are very old: Corsair Pro Series 650W, Intel DZ68DB, and Intel i5-2405S. The motherboard is brand new and the other two are only a few months old.

Any of the three components could be causing the processor core voltage ripple, but I think the PSU is the most likely suspect. But it could be the CPU. Unfortunately I never noticed if the ripple was occurring when the PSU and CPU were on the previous Intel motherboard (I am not thrilled about ripping it all apart and switching motherboards for a test).

Do we have any electrical engineers here who could share a few thoughts on PSU fluctuations and what they mean? How bad does ripple need to be to be serious? And how out-of-spec do voltages need to be to be serious?
March 5, 2012 2:19:59 PM

Time to bring out the multimeter and see if I can recreate what Intel Desktop Utilities is telling me.
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March 5, 2012 2:36:39 PM

It is adjusting the core voltage in relation to load/CPU frequency, which is normal.
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March 5, 2012 2:49:02 PM

indeed, very normal. its a power saving tool. also, your 3.3v reads are fine also. you only need to watch those when they start to dip below the rated 3.3v spec. (even 3.2-1 would be fine) however, psu's do begin to degrade over time, so dont really expect it to last forever. now, your psu is a quality unit, so i wouldnt expect anything in the near future.

what spec is your ram rated to run at? if its rated at 1.5v, i wouldnt worry too much there either.
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March 5, 2012 3:42:10 PM

Jim_L9 said:
It is adjusting the core voltage in relation to load/CPU frequency, which is normal.


That would be true if the system was actually running something. However, the readings I gave were taken when the system was doing nothing at all, with not even a browser running. The antivirus had already updated and TaskManager showed 0-1% CPU activity.
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March 5, 2012 3:44:00 PM

guavasauce said:
indeed, very normal. its a power saving tool. also, your 3.3v reads are fine also. you only need to watch those when they start to dip below the rated 3.3v spec. (even 3.2-1 would be fine) however, psu's do begin to degrade over time, so dont really expect it to last forever. now, your psu is a quality unit, so i wouldnt expect anything in the near future.

what spec is your ram rated to run at? if its rated at 1.5v, i wouldnt worry too much there either.



It has 16GB of Corsair XMS RAM, four 4GB sticks rated at 1.5v.
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