CPU runs fine without 12v supply?

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daddyruffe

Thread Starter
Joined
Dec 31, 2005
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20
I've just noticed that one of my systems has been running fine for over a year and I'd forgotten to connect the 12 v lead on the PSU.

Does it actually make a difference? I thought the system would not boot without the 12v supply to the CPU?
 
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Apr 27, 2004
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4,719
12v lead to the cpu? Cpu gets its power from the 20pin plug on the motherboard.
That plug Is probably a cpu senser or heatsink fan speed regulater.
 

ETS

Joined
Oct 13, 1999
Messages
972
I think you are talking about the extra 4 pin 12v connector that is used by Pentium 4 motherboards.
This doesn't actually feed 12v to the cpu, but rather to a voltage regulator on the motherboard. The Pentium 4 derives some of its power from this, but not 12v. This does free up more 3 and 5 volt power to the rest of the system.
As you have seen, it is not always required.
My system at home, for example, will not boot without it.
 
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I thought it was near the cpu thats why I didn't mention the 12v four pin plug, Ia'm not sure the computer would boot correctly without it, then I have never tried.
 

JohnWill

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Oct 19, 2002
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106,531
Actually, that 12V plug and the 12V from the standard 20 pin P/S are commoned on the MB. However, due to the high current requirements for the Pentium switching regulator, this extra direct feed was added. While it's running without it, it will be more reliable with it connected properly.
 
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