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cpu voltage

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mirko_3

Member
Joined
Oct 27, 2002
Location
Italy
I never really gave this a thought, I just knew it was true and never really thought about it, but now I'm curious: can anyone explain to me why it is that the cpu voltage gets lower while under load the while idle?
 

JaY_III

Senior of BX
Joined
Dec 17, 2000
its more of a PSU/voltage requlator issue that a CPU issue...

as when a CPU is under 100% full load (or any load for that matter) it draws more power. Now that the CPU is drawing that much more power, the PSU has to work that much harder. The lower the quality of the PSU/Voltage regulator the more of a drop you will notice.

Even high end PSU's will still let the CPU drop in voltage a little, and the more loaded the PSU is, the more this will happen.
 
OP
mirko_3

mirko_3

Member
Joined
Oct 27, 2002
Location
Italy
oh, ok; so basically the cpu doesn't always draw the power it should... oh, and aren't there supposed to be 'things' (don't know what they're called) on the motherboard that are supposed to minimize this change it voltage?
 

JaY_III

Senior of BX
Joined
Dec 17, 2000
Voltage regulators are the things.
PSU has them and so does the motherboard....
Cheaper MB's and PSU's have cheaper regulators and thus a less constand voltage.

Moden CPU's and OS's have HLT (halt) instructions built in so that they idel the CPU when not in use. It is almost tuning off the portion of the CPU not being used to save power/prevent overheating/overuse.
As a CPU will now only draw it max power under full load.
 
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mirko_3

mirko_3

Member
Joined
Oct 27, 2002
Location
Italy
jay said:
Voltage regulators are the things.

well now, that's an inventive name :)
ok thanks, I know what HLT commands are, I just never thought of how they could influence cpu voltage...
Thanks a lot, everything is clear now...
 

ElroyCarbon

Member
Joined
Apr 10, 2002
Location
Racine
Damn I really never noticed, but mine drops from 1.63 down to 1.55 and then planes out at 1.57. Is this average? That is when I initiate "Folding" I mean hell I'm running an Antec True power 550, if this can't handle the diff what can. I'm guessing this is OK cause of the fact Folding takes so much from the CPU although I would expect the PSU to compensate and make of the deviance, HMM
 
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mirko_3

mirko_3

Member
Joined
Oct 27, 2002
Location
Italy
well, changes in voltage depend a lot ( i think mostly) on the motherboard... but 1.63 to 1.57 isn't something THAT bad, actually on some motherboards it's standard...