I've only recently learned that on current motherboards, the cpu is actually using voltage from the +12V rail, and not the 3.3V rail, but older cpu's used the 5V or 3.3V rails. Does anyone know the exact source for each class of cpu or a resource where I could find the info?
I'd llike to learn for early Duron, K6II 500, socket 370 Coppermines, PII's, and Pentium MMX.
Which Voltage rail used by cpu's?
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dukla2000
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I think all of those older CPUs you list will have mobos that generate the CPU VCore from the +5V power rail.
The move to using the +12V rail was triggered by the P4 design guide/requirements so all (I think) P4 mobos use +12V and possibly a very few other Pentium mobos that have been designed since the P4 hit the streets.
It seems ALL Athlon 64 mobos will use the +12V: most earlier Athlon (socket A) mobos have used +5V with a reasonable number of recent exceptions (like my KT6) to prove the rule.
Beyond these generalisations there is no simple source for you to reference: it is a feature of mobo design and the standard mobo publications don't highlight VCore regulation methods.
The move to using the +12V rail was triggered by the P4 design guide/requirements so all (I think) P4 mobos use +12V and possibly a very few other Pentium mobos that have been designed since the P4 hit the streets.
It seems ALL Athlon 64 mobos will use the +12V: most earlier Athlon (socket A) mobos have used +5V with a reasonable number of recent exceptions (like my KT6) to prove the rule.
Beyond these generalisations there is no simple source for you to reference: it is a feature of mobo design and the standard mobo publications don't highlight VCore regulation methods.