Which rail give the CPU the power?

[steimm]

Hi there!

I wonder, which rail is giving the CPU power?
I've been getting different information from alot of places, everything from the +3.3V to the +12V. What is true?
Is it depending on the CPU, I mean is it a difference between a PII, PIII, P4, T-bird, Palomino, T-bred etc?

Can someone tell me?

/steimm

 

[overdoze]

usually the 5V rail. There are exception for the dual cpu setup or new cpu

 

[spazzkid]

i agree, its the 5v rail.

 

[steimm]

Thx, so then it is most important to have high Ampere on the 5V-rail if I've been voltmodding the Vcore on my motherboard?

/steimm

 

[spazzkid]

yes more amperes the better, like 40amps and above.

 

[DaveSauce]

oh wow...i just noticed that my p/s can take up to 50 amps to start up....im surprised my house doesnt dim when I start this thing up....

 

[Gemini1706]

The CPU uses the 12V rail in the Athlon case. Do not know about the Pentium.

The 12V is regulated down to vcore voltages using a built-in regulator in the mobo. I think the 12V line is used becasue you can get alot of power from the supply with lower current (becasue power=Voltgae*Current, ofcourse somw power is lost as loses and heat).

 

[equalizr]

That would be a 500W power supply!!...no one needs that unless they are running like dual AMD and 4HDD's and 40 fans

yes more amperes the better, like 40amps and above.

 

[DaveSauce]

P4s use the 12 volt rail and another 12 volt 4-pin thingy...I think that is also for the CPU...but it might be for the rambus or somethin, lol, I dunno....its only used on P4 mobos tho.

 

[overdoze]

oh wow...i just noticed that my p/s can take up to 50 amps to start up....im surprised my house doesnt dim when I start this thing up....

high wattage will dim your light like 800W or above. High amps does not mean it is high wattage. Most typical PS draw somewhere in the 200W range.

 

[Sonny]

I know it to be the 5V rail but AMD sometimes says its the 12V rail & so does THG(LOL) but when my 'puter goes from idle to load I see my 5V drop a little & my 12V jump a little so I believe it to be 5V plus AMD also said that their 2GHz plus chips will need 45A on the 5V rail for it to even run stable now Abit(don't follow the other brands as much) adds a 12V socket on their newest chipset just like on P4 systems. I still think it's the 5V rail.

 

[juliendogg]

i'm goin with sonny on this one, it's my understanding that the cpu is powered off the 5v rail. hence the massive problems that can come from a low 5v rail. my system reboots instantly if the 5v drops to 4.75. does that on occasion as i'm still using an old 250w psu. at idle it's ok, 4.89. not so bad. put the cpu under 100% load and down it goes. usually stops around 4.79 and stays pretty stable. new psu in route