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Setting Voltage for overclock E6750 + P5K

silvercut

silvercut

silvercut

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Joined
11 Sep 2008
Posts
608
I am currently running an unstable overclock of 3.6ghz (450*8). I try to set the cpu voltage (to e.g.1.375 or 1.4V) manually on the mobo but when I boot up on CPU-Z it shows 1.344V and PC crashed/halts when run prime.

When I let the CPU voltage to be automatic it sometimes sets the voltage at 1.4v and sometimes as 1.36-1.37 and is usually more stable.

I am running RAM pc2-6400.

Any advice ?
 
What's the VID?

My E6750 has a VID of 1.35 and i've only got it to 3GHz stable, it would need more than 1.43V to go beyond that, which I wasn't comfortable with for the long term.

System crashes under prime are not usually the CPU however, almost certainly not if it boots OK. Have you clocked the RAM? What's it running at and with what timings?

This could also indicate a problem with the power supply, what make/model do you have?

The voltage being different in the BIOS may be caused by intel speedstep function that underclocks the CPU when it's not loaded. Check in the BIOS this is disabled (speedstep or maybe C1E iirc).

Only other thing I can think of is you're suffering large vdroop.
 
alexhull24 said:
What's the VID?

My E6750 has a VID of 1.35 and i've only got it to 3GHz stable, it would need more than 1.43V to go beyond that, which I wasn't comfortable with for the long term.

System crashes under prime are not usually the CPU however, almost certainly not if it boots OK. Have you clocked the RAM? What's it running at and with what timings?

This could also indicate a problem with the power supply, what make/model do you have?

The voltage being different in the BIOS may be caused by intel speedstep function that underclocks the CPU when it's not loaded. Check in the BIOS this is disabled (speedstep or maybe C1E iirc).

Only other thing I can think of is you're suffering large vdroop.
Click to expand...

I have 500W PSU.

Ram 800Mhz stock is running at 900Mhz (450mhz) 5-5-5-15...which might be the issue.

I have the cpu stable at 3.2Ghz and at 3.6 it is also seems stable until i run prime and then it just freezes and i have to restart pc.

All that other stuff is disabled.
 
Try setting the RAM as close to 800 or below and then try again. The overclock might be the issue.

What make/model RAM and PSU?
 
alexhull24 said:
Try setting the RAM as close to 800 or below and then try again. The overclock might be the issue.

What make/model RAM and PSU?
Click to expand...

ram is GEIL Ultra - PSU is antec earthwats 500w.

This is the error on prime when I do a CPU test on core0:

Test 1, 800000 Lucas-Lehmer iterations of M172031 using 8K FFT length.
FATAL ERROR: Rounding was 0.5, expected less than 0.4
Hardware failure detected, consult stress.txt file.
Torture Test ran 0 minutes 0 seconds - 1 errors, 0 warnings.
Execution halted.
---

Also when I do belnd test for cpu and ram the tests dont seem to iterate they just stay in test 1. and it only tests the ram and not the cpu.
 
You should get the dual core version of prime, I believe it's available from the makers website, if you don't have it already.

Is this still happening with the RAM underclocked?
 
alexhull24 said:
You should get the dual core version of prime, I believe it's available from the makers website, if you don't have it already.

Is this still happening with the RAM underclocked?
Click to expand...

OK Now I am using PC2-8500 RAM (kingston hyperx) which is underclocked and running at 900Mhz so I have 450*8 =3.6Ghz.

FSB:Memory 1:1 - 5-5-5-15

The system seems stable for general use but it just can get past orthos stress testing:

Test 1, 4000 Lucas-Lehmer iterations of M19922945 using 1024K FFT length.
FATAL ERROR: Rounding was 0.5, expected less than 0.4
Hardware failure detected, consult stress.txt file.
Torture Test ran 0 minutes 37 seconds - 1 errors, 0 warnings.
 
You've taken a similar course to me. Having thought it was the memory/board it turned out my CPU needed a lot more volts than I thought. Considering I can only get to 3GHz on what i'd call a 24/7 voltage, unless your chip is miles better 3.6 might be pushing it. Just try upping the voltage on the CPU until it's stable.
 
The problem is setting the voltage manually because whatever voltage I put in BIOS for the CPU when I boot up it's a completely different voltage. So I set the voltage to 1.4v for example and when I booted up on CPU z it was showing 1.368.

I am running bios 1201 so maybe there is somehitng wrong with this bios when I try and set the voltage.

This is why it is faling the stress testing.
 
That's somewhat normal, it's called Vdroop. It's when your CPU voltage goes lower than the set value due to stress and passing through mosfets.

Or something like that! :)
 
As I said in my first post, you may well be suffering large vdroop. Have you tried setting the voltage higher still to test this? 1.45V on a conroe should be within the realms of acceptability, then you can check the stability and look at reducing the voltage to a point where you can get a clock you're happy with.
 
Ok I set the voltage to 1.45 on the mobo but when in cpu z this gets down to 1.4 which is still good but then when I run orthos the vcore drops from 1.4 to 1.35 and the orthos fails.

Load line calibration has been disabled by the way.
 
Even with LLC enabled vdrop is still bad. It goes from 1.432 idle (cpu-z) to 1.376 under load.

But apparently the vdroop is terrible with the p5k non-premium boards so I have been doing research and there is this pencil vdroop mod which I will do meaybe on the weekend see if it improves the vdroop.
 
Yeah that's exactly what I was going to mention. LLC doesn't do much btw, sometimes it even makes the system less stable, so if it's the same without may as well leave it off.

Look into the pencil mod and see where that gets you, otherwise, if you want to push further, you'll have to get a newer/better board I would have thought.
 
silvercut, what P5K mobo you have?
I overcloacked my E6750 to 3,8GHz without VoltMod in BIOS, maybe I had really nice copy :) Try to set NB voltage higher, its very powerful config. And what is your CPU cooler? I didn't catch...
 
The mobo is just P5K (standard aka vanilla) I haven't played around with the NB voltage and haven't done the pencil mod yet. But I've got it stable 3.6ghz @ CPUz-1.456 (no load) -> 1.384 - 100% load.

Is it ok to keep it at that voltage for 24/7 use i.e. will it drastically reduce CPU lifespan ?

p.s. what nb voltage are you using for yours ?
 
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Mmm... silvercut, your Voltage is too high I think... Q9550 is 45nm proc -> you have Volt like Q6600 old step :D My prime interest is your temp for cores. ? High temp = less proc life :) But it can works for 5-10 years without crashing, Conroe is LongLife chip.
Your CPU cooler is...?

As for me, my voltages: IDLE - Vcore 1,304V, LOAD - 1,296V. But the temps are terrible - 47 Idle, ~70 Load. Awful result for TT BigTyp 120 :( But I have 3,83GHz frequency :)
 
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