How much voltage can I safely give a water cooled 640?

Killaapp · Jan 3, 2006

Hey guys,

I just recently installed water cooling on my P5AD2-E rig to cool my 640. The chip is stable at 263fsb at 1.425volts (in bios). Load temp is about 33-34c.

I recently bumped the fsb to 270 and increased the volts to 1.475 (in bios) and still was not dual prime stable. When the bios was set to 1.475volts it delivered about 1.416 volts under dual prime load. Chip was 35c under load.

My question is, what is the safe max voltage I can feed this processor, and should I base that off the bios setting, or the load voltage.

I have zero experience with Prescott's under water cooling, any advice would be great.

Thank you

hUMANbEATbOX · Jan 3, 2006

while i don't know from first hand experience, judging by ppls sigs and personal accounts from a few forums, 1.5-1.55 should be fine. your 775 mobo is much more robust than you 478 mobo. afaik, on 775 your real limits should be temps, not so much on the vcore.

someone with 775 knowledge needs to hop in here

larva · Jan 3, 2006

I think you are being excessively conservative. The default VID of my P4 506 is 1.4V, so I don't lose a moment's sleep running it at 1.5V if required. My particular chip requires 1.44V loaded Vcore to completely stabilize at my 4GHz target clock rate, and it will live essentially forever at that voltage.

Although it is repeated often enough, the notion that cooling allows more voltage before damage occurs is just a myth. Electromigration is the damaging agent, and is accelerated by increases in Vcore, radical cooling or stock. That being said, the design of the Prescott is sanctioned for use to 1.4V by no less an authority than Intel themselves, so increases to 1.5V are unlikely to produce consequences that can be noticed in the useful lifespan of something like a PC microprocessor.

As far as which number is the correct one, none of them are, in most cases. You must measure the actual Vcore with an accurate voltmeter if you wish to pinpoint any number as being any more reliable than the next.

Killaapp · Jan 3, 2006

ok thanks, I am just confused because setting my bios volts to 1.475 gives me 1.5volts at idle and 1.416 volts at load. I know the proc can probably hand at least 1.45 volts at load just fine, but that would require setting the bios to roughly 1.525 volts, which may yield 1.55volts at idle.

I have a fan on the window of my case flowing over the mosfets so I am hoping the motherboard's power management is adequately cooled. I also removed the stock thermal compound between the mosfets and the copper heatsink and added some Arctic Silver Ceramique.

I'll attach a picture to show my config.

Killaapp · Jan 3, 2006

Larva - thank you, I most def need to get my hands on a volt meter. I will try to run the chip at bios 1.5v and see if that allows me to stabilize at 270fsb.

batboy · Jan 3, 2006

Go ahead and bump the vcore to 1.5v in the BIOS. If it bounces to 1.55v at idle, but pulls down under load, you should be fine. I run my Prescott at 1.5v almost all the time and often bench at 1.55v.

Killaapp · Jan 3, 2006

Batboy - thanks a bunch for the info, I am going to try for 1.5v tonight and see if I can hit 270fsb stable.

Alchemy1 · Jan 3, 2006

I'm kind of late, but yeah I use 1.51v (actual) on my chip. I wouldn't hesitate to go up to 1.55v actual either.

Killaapp · Jan 4, 2006

Thanks for the help guys - 1.5v in bios and I am so far 12 hours prime stable at 270fsb

Alchemy1 · Jan 4, 2006

Wow...nice chip!

Killaapp · Jan 4, 2006

Thanks Alchemy1, I was originally worried because the chip was made in China. I have never had great experience with China chips and spent a long time trying to buy a Costa Rica chip off someone.

I can't run 275fsb at 1.5v, nor 1.5125v. I am nervous about going to 1.525 for normal use, so I'll probably soon find my max between 270 and 274 fsb.

It's a shame because my ultimate goal was 275 x 16 = 4400mhz with ddr2-733.

Alchemy1 · Jan 4, 2006

I hear ya man. My china chip is running at 4.1ghz stable @ 1.51 actual volts. It is not great, but I plan on getting a 65nm chip once they become avaliable and people start giving their results.

xTrEmEoVrClOcKr · Jan 4, 2006

I hear you, cannot wait til I get rid of my 650 / get a 661.

dylskee · Jan 4, 2006

Nice setup Killaapp, that's a pretty good clock also! I'm planning on a water cooling setup myself soon so i was curious as to how much voltage would be safe for H2O also, looking to hit 4.4GHz myself.

Shelnutt2 · Jan 4, 2006

Thread Hijack>
Dylskee I love your avator

</Thread Hijack

Killaapp · Jan 4, 2006

dylskee - that is a fun avatar haha

I'm sure 4400mhz will be well within reach with your 650.

xTrEmEoVrClOcKr - that is going to be a fun chip, can't wait to see the results you get with it.

fordf250 · Jan 4, 2006

I ran my 640 at 270fsb with 1.65V on air 24/7 for two months never a problem. Im running dothan right now but will be putting the 640 in a 975 chipset mb to see how far it will go 270 was the max on the 875p-t.

batboy · Jan 4, 2006

Personally, don't think I would go above 1.6v.

NODES · Apr 25, 2006

batboy said:
Personally, don't think I would go above 1.6v.

ive tested over 1.6V

but im under the tap

How much voltage can I safely give a water cooled 640?

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