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Undervolting a Q6600 - how low is too low?

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  • CPUs
  • Overclocking
Last response: in Overclocking
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December 28, 2007 12:27:28 PM

My CPU is a Core 2 Quad 6600 B3 running at stock 9x266 2.4 Ghz with a 1.325 VID. I've been lowering its voltage in increments of 0.00625V using the Gigabyte Easytune 5 tool that came with my GA-P35-DS3L motherboard, then testing in prime95 for 5 minutes in small FFT mode, then lowering the voltage again to see how low it will go before it crashes, so I can bump up the voltage and get it stable. So far I'm at 1.09375V (CPU-Z says 1.026V), and haven't reached my crash voltage yet. This seems to me to be an extremely low voltage. Is it safe to continue lowering the voltage? If I continue my undervolting tests and go too low, could I end up damaging my processor?

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December 28, 2007 1:52:16 PM

You probably won't damage it, but you should be letting Prime run for longer than 5 mins. Sometimes, you won't see errors until hours have passed. Keep it where it is right now and stress it for 24 hours. If that is stable, then notch it down, and repeat.
December 28, 2007 3:36:39 PM

My motherboard has about 52 voltages between 1.325V and 1.0V. To stress test all of them for 24 hours would take 52 days.

By lowering the voltage in increments of 0.00625V and then doing prime95 for 5 minutes, I'm trying to find the exact voltage at which the computer isn't even stable in prime95 for 5 minutes. then when i find that voltage, i can bump it up a notch, then run prime95 for hours and hours until I get it 100% stable in prime95 for 24 hours.
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December 29, 2007 3:58:13 PM

i think what he means is that ever 15 or so of those increments you should do a 24 hour stress test, and in between each of the lowerings you should continue to do the 5 minute tests.
December 29, 2007 8:05:37 PM

Why don't you start at 1.0V and work your way up?
December 29, 2007 8:18:30 PM

What I mean is, Prime 95 uses different test parameters for each test. Larger values, different data strings, etc that will affect the processor differently. If you watch your temps, you will see what I mean. Some of the test scripts will only peak my CPU around 61c.... However, some of them will spike up to 67c. Obviously, something different is going on there that might require an even stricter voltage tolerance. So, even though you may be OK for the first 5 mins, once those certain tests run that obviously hammer the CPU harder kick in, it could blue screen or simply throw an error.

You could be wasting more time using your current method than you think. Do what Spud said and every 15 or so increments, run it for 24. It might save a lot of time in the long run. You could already be too low and not know it.
December 29, 2007 8:38:04 PM

Well if he crashes within the first 5min, he'd increase it maybe by 2 increments. Then he'd test that for 24hours. If it crashes, increase it by another 2. Any crashes after that, just increase it by 1.

That's probably what he's doing, and frankly I think it's better.
December 30, 2007 3:42:09 PM

I started testing again, and at 1.075V I got an error in Prime95 after 5 minutes, so I bumped it up to 1.08125V and got an error in Prime95 after 2 hours and 30 minutes. So I bumped it up to 1.0875V, and then I got an error after 2 hours and 21 minutes. Then I bumped it up to 1.09375V, and it's been running Prime95 now for 8 hours with no errors.

edit~
Wow, Prime95 detected an error after 23 hours and 32 minutes, just as I was thinking that 1.09375V was my magic number. On to 1.1V.
December 31, 2007 1:58:34 PM

I thought the least time for 'official' stable was 8 hours as mentioned in the guide. Anything paste that is just a nice way to up the electric bill. But basicly just pick a voltage you think it will be stable at(start from the lowest you think will be stable). Run the prime test for 8 hours (overnight) Depending on how long it took to fail, say it only failed after an hour, increase the voltage by 3 steps,repeat. If it lasted say 4-6 hours up it by 2 steps and call it good. Personally this is what I did but a little more lazy. I got a lucky pick and the prime test ran for about 3 hours. So I upped the Vcore by I think 1 or 2 steps and never looked back. Never had random lockups/BSOD or anything like that.
March 23, 2008 3:08:09 PM

i have the G0 stepping of the q6600 and i have it running stable at 1.048V
March 24, 2008 1:36:43 AM

Thanks for the input, you're just 3 months late.
March 24, 2008 5:12:29 AM

Who's the guy with the Mario giving the princess a Italian salami?
March 24, 2008 9:40:24 AM

let us know how you did.i wanted to do some under volting and underclocking as well!to save me some money when im abit tight!lol

i guess i will turn my monitor brightness down as well along with my fan on the case and cooler!lol damm!!!then i must be so so tight!HAHA
March 24, 2008 9:47:48 PM

iluvgillgill said:
let us know how you did.i wanted to do some under volting and underclocking as well!to save me some money when im abit tight!lol

i guess i will turn my monitor brightness down as well along with my fan on the case and cooler!lol damm!!!then i must be so so tight!HAHA

what does moniter brightness have to do with anything?
March 24, 2008 10:03:04 PM

well it draws power doesnt it?lol
!