Intel i5 750 overclocking fail? Prime95 errors

Hello!
I'm trying to overclock an Intel i5 750 2,67Ghz but it doesn't seem to work. I'm using a Gigabyte GA-P55M-UD2 mainboard which should be quite suitable for overclocking though... and Windows Server Edition 2008

I'm testing the stability of the system with Prime95, Blend-Test, but no matter which setting, even with the default setting (@2,67Ghz!) there would be an error message after a few minutes and one or two cores would stop working.

Most interestingly the frequency of these errors seem to be dependend on the clock and voltage settings... At least in some settings these errors appear later than in others.
Also I'm having no troubles getting the system started, no matter which voltage settings I use - it would even start on standard voltages @4,0 Ghz but the Prime-Test would fail immediately (actually its always two cores that fail, while the others would continue working, but not the same cores every time)

What's the reason for that? And what does it mean?
Anyone who's got any ideas?

 

Just one more note:
Before I did the blend tests, I did the "small FFTs" Test, and I got some apparently stable settings right away... (I tested only for 10 minutes).
But with the Blend Tests errors occur after less than 4 minutes, no matter which setting i chose..

The most stable Settings at the Small FFTs tests were:
@3.33 Ghz, BCLK Freq: 166Mhz, Multiplier: 20x:
Standard Voltages

3,99Ghz, BCLKFreq: 190Mhz, Multiplier: 21x:
VCore: 1.375V, QPI/VTT: 1.35V, PCH: 1.12V, CPU PLL: 1,9V
VCore: 1.3625V, QPI/VTT: 1.35V, PCH: 1.12V, CPU PLL: 1,9V
VCore: 1.3625V, QPI/VTT: 1.35V, PCH: 1.05V, CPU PLL: 1,9V
VCore: 1.35625V, QPI/VTT: 1.39V, PCH: 1.12V, CPU PLL: 1,9V

all these settings would fail in the Blend Test in less than 2 minutes.

This setting did the best in the Blend test (still only about 4 minutes):
@3,6 Ghz, 180Mhz, Multiplier: 20
VCore: 1.3625V, QPI/VTT: 1.37V, PCH: 1.12V, CPU PLL: 1,9V

 

What type of cooling are you using? Are you sure it's seated right on the processor?
And how are your temps?

 

Hi!
It's not a temperature problem. I use an Arctic Cooling Freezer 7 Pro, not the best Heatsink, but still good enough. The temperature max. is about 76°C @ 4Ghz. But as I said, the prime test would even fail in stock settings! so if I run the procesor @2,67 Ghz with no overclocking whatsoever the Blend Test would still fail!

 

If you get errors in blend and not small FFTs then it's likely a memory stability issue. But you should run Prime for longer to be sure.

What RAM and RAM divider are you using?

 

It's 4GB DDR-3 1333Mhz (2x 2GB). It says 9-9-9@1.65V
The default setings are 1333Mhz, 1,5V, Channel Interleaving: 6, Rank Interleaving: 4
I could tell you more details tomorrow!

even in the default settings 2 cores would just hang up after 5 minutes.
I've heard from people having similar problem in other forums... but no solutions there...

 

About the Ram:
Its OCZ Gold series, PC310666, 1,65V, Timings: 9-9-9-20, 13333Mhz, 2x2GB.
The memory is set correctly, still the blend test fails after seconds on standard frequency!

 

Use memtest and test your ram sticks individually one at a time
http://www.memtest.org/
Once you have downloaded memtest,burn it to cd/dvd and reboot your pc with the cd/dvd in the drive,also make sure that you set your pc to boot from cd/dvd in the bios...memtest will then start working for you as soon as you reboot

 

Ditto on giving Memtest a shot.

I also have a 750 (as you may have noticed), and I was going to mention how they tend to need quite a lot of volts in order to get decent overclocks, but to fail Prime95 at stock does seem very strange.

It is likely to be your RAM.

 

Memtest produced 2 errors.
The RAMs are completely new - is it still likely that they are broken?
I'm going to try it with different RAM modules - but what if I still get errors? Is there anything I could tweak in the BIOS?

 

First you'll want to find ALL the settings of your memory, likely from the manufacturer's website or tech support, and manually enter them into the BIOS.

Sometimes the motherboard doesn't detect the RAM correctly, sets the wrong timings, unstable RAM.

 

Try all your ram at stock settings(basic) and run memtest once again with each stick individually in each slot.About 1 hr per stick.

And yes you can get ram that is faulty,your motherboard maybe faulty,but dont worry as long as you have guarantee on your hardware you can change it....i had same problem in april this year,i sent my board and ram back just to be sure,got my replacement stuff in about 4 weeks in total.

 

Now I ran Memtest and the Prime95 Blend-teston several configurations and received some funny results:
Both DIMMS intalled: 2 errors on Memtest, Prime95 Blend-test fails.
DIMM #1 (no matter on which slot): No errors on Memtest, no errors on Prime
DIMM #2 (no matter on which slot): No error on Memtest, Prime fails

Seems like one of the RAM modules is faulty, still funny that Memtest doesn't show any errors... Is it still likely that I will get replacement? I guess the retailer will also test it before doing a replacement, and if Memtest or something similar is beig used then, it would look like the module was okay....

 

Good news!
I replaced the RAM that produced errors at no extra charge and no the machine runs neatly... No stability issues @3,5 Ghz, I didn't try 4Ghz yet, but as the rig is going to run 24/7 I think I'll stick to lower clock speeds...

Thanks for your help everyone!

 

ok well done

 

Well if you're even thinking of going for 4Ghz on a Freezer 7 Pro, then i reckon you're asking for trouble tbh.

 

I've had my i5 750 @ 4GHz for 5 months 100% stable, I had no problems at all.

 

I really don't think you will need that many volts for a 4GHz overclock. I'm currently running 1.325v (in the BIOS), and unless I have a really good chip (or you have a really bad one), I don't see 1.5v being a good idea. Even 1.45v seems excessive. Aidan777 also has his at 4GHz and it is using a tad under 1.4v

Seeing as temps go up exponentially with voltage, you really want to use as little as possible.