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Can any PSU run any CPU, regardless of CPU wattage & PSU specs?

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July 1, 2012 5:54:07 AM

Hello all..

My question is can ANY good PSU run any CPU? or it's like GPUs, the PSU has to be powerful enough to handle the GPU?

I'm asking because I used to run an AMD 125w CPU on a PSU the has these spec..
+3.3v(18A)/+5v(25A) -- 160w
+12v(18A) -- 216w
390w PSU


Because I wanted to get a strong GPU, I exchanged my PSU for this one
+3.3v(24A)/+5v(20A) -- 120w
+12v(34A) -- 408w
500w PSU

And I just noticed that the wattage on +3.3/+5 is 120w, while in my old PSU it was 160w

I was wondering if this would make a problem running my 125W CPU

note: my mobo is currently down, so I never tested the new PSU on the 125w CPU


Thanks in advance
a c 191 à CPUs
July 1, 2012 6:02:25 AM

Im not going to answer your question because it depends on too many factors and gets complex really quick.


But, for what you really need to know it just comes down to what systems use what kind of power, your CPU is entirely powered from the 4 or 8 pin CPU power connector which only provides power from the 12 V rail, your CPU uses most of its power from the 12 V rail, it gets a small amount from the 3.3 V and 5 V rails for it's integrated circuitry on the board but most is from the 12 V supply. Hard drives, optical drives, and RAM use the 3.3 V rail and 5 V rails to power their main logic circuits and to provide all the power for the RAM, none of these devices require much power hence new PSUs tend to provide limited power on the 3.3 V and 5V rails but quite a bit on the 12 V rail since that is where most of the power draw is from.

The new PSU won't have any trouble running your CPU.
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July 1, 2012 6:24:54 AM

Thank you very much hunter315.. that was really helpful.

So these 120w will be enough even if I took it as far as I can? (like five 7200 HDDs, 32gs of RAM)??

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a c 191 à CPUs
July 1, 2012 6:32:38 AM

The RAM draws limited power, especially DDR3, and the main power consumption of an optical drive and hard drive is the motor which is usually powered off the 12 V rail. 4 sticks of ram will pull maybe 20 W, the drives combined will pull maybe 40 W between the 5 V and 3.3 V rails. It is really hard to overload the minor rails on a power supply, most devices with significant power consumption in a computer draw their power from the 12 V rail since there was the change to that being the dominant rail during the pentium 4 era.
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July 1, 2012 2:48:31 PM

Best answer selected by hunted22.
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July 1, 2012 2:49:04 PM

thank you hunter315
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December 23, 2013 1:06:24 PM

hunted22 said:
thank you hunter315


Hi, sorry to the forum as I know this is an old thread, but I'd like to know if it was a sucess, hunter22, and the forum gives a 404 if I try to send you a private message.

Was it a success, hunted22? I have a similar system and a similar problem with a Pentium 4 system configuration and with very low wattage PSUs in the combined rails in the market to choose. Just 120W for a P4, 7600GT AGP, 4 PCI, 5HDDs and 4 RAM sticks, looks to be in the edge.

I hope this reaches you as an email notification and you can answer me :-)

Regards.
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a b à CPUs
December 23, 2013 2:55:56 PM

hunter315 said:
Im not going to answer your question because it depends on too many factors and gets complex really quick.


But, for what you really need to know it just comes down to what systems use what kind of power, your CPU is entirely powered from the 4 or 8 pin CPU power connector which only provides power from the 12 V rail, your CPU uses most of its power from the 12 V rail, it gets a small amount from the 3.3 V and 5 V rails for it's integrated circuitry on the board but most is from the 12 V supply. Hard drives, optical drives, and RAM use the 3.3 V rail and 5 V rails to power their main logic circuits and to provide all the power for the RAM, none of these devices require much power hence new PSUs tend to provide limited power on the 3.3 V and 5V rails but quite a bit on the 12 V rail since that is where most of the power draw is from.

The new PSU won't have any trouble running your CPU.

you said that hard drives and optical drives use 3.3v rail? Most hard dives and optical drives use molex or sata connectors. molex uses 12v rail and 5v rail. sata connectors use 3.3v, 5v and 12v rail but 3.3v is almost never used. i dont actually know any sata device that uses 3.3 rail. laptop hdd's use 5v and desktop hdd's use mostly 12v and some 5v
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