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Intel Core i5 750 OC problem

post #1 of 3
Thread Starter 
For starters hello everyone. I've only just found out of this forum and it looks to be a very interesting place.

I have an Intel Core i5 750 over an Asus P7P55D M/B. I recently tried OCing it to get as close as possible to 4.0GHz. I ended up at 3.8GHz (181x21, 1.328V) which run Prime95 (Win7 64bit) successfully for 24hrs before manually terminating the test. A Memtest86 pass also confirmed memory stability and the temps are reasonable. From all accounts I have a stable OC, but for one thing.

When attempting to run Linux (Ubuntu 10.10, kernel 2.6.35) I got an MCE leading to a kernel panic and a restart before the login screen had a chance to display. This error was 100% repeatable and appeared to be tied to the CPU clock. I could boot with 181x20 and with 156x21, but not with 161x21 or higher BCLK.

This issue has me a bit baffled because on the one hand MCE is a hardware error, but on the other I only experience issues with a particular O/S. Win7 runs fine as does Ubuntu 10.10 with 2.6.34 kernel. I tried compiling the 2.6.37 kernel but it didn't help. Installing the latest BIOS similarly had no effect (Other than the fact that I can now no longer activate SpeedStep above a certain BCLK which is a good thing stability wise. The problem was worse with SpeedStep on.).

Right now I'm running at 156x21 and software OCing to 181 using Asus TurboV Evo which is obviously a less than optimal solution.

I would appreciate any ideas that might help me troubleshoot this.

PS: Here is the MCE code I captured after one of the last tests I run:
Code:
HARDWARE ERROR. This is *NOT* a software problem!
Please contact your hardware vendor
MCE 0
CPU 0 BANK 5 
MISC 1 ADDR 3f1c855701c6 
TIME 1295007898 Fri Jan 14 14:24:58 2011
MCG status:
MCi status:
Uncorrected error
Error enabled
MCi_MISC register valid
MCi_ADDR register valid
Processor context corrupt
MCA: Internal Timer error
STATUS be00000000800400 MCGSTATUS 0
MCGCAP 1c09 APICID 0 SOCKETID 0 
CPUID Vendor Intel Family 6 Model 30
PS2: I tried contacting Intel to get a decode of the above log, but to no avail. The employee I spoke to on chat didn't even know what MCE was.
post #2 of 3
First the MCE is a linux kernel boot error I believe. Therefore Intel would have no idea what it meant. I am in no way competent to give any Linux advice though.
If you are dead set on running Ubuntu or a variant, may I suggest Zorin 4. I run it myself and like it.
I also have had difficulty setting memory clocks and overclocking my I5. Try backing down the multiplier to 20, and try different settings of 195 or so and back the core voltage to under 1.3v. Be sure and raise the VTT to at least 1.28v. Also, I had to back off from 1600 Mhz on the memory to get the system stable.
Here is a link to my most stable overclock yet.http://www.flickr.com/photos/5806599...40/lightbox/#/
My Mobile Beast
(16 items)
 
  
CPUMotherboardGraphicsRAM
I5 750 @3.809 Ghz MSI P55-GD85 XFX 5850 @ 801/1150 38c idle 8 GB Corsair XMS3 1600 Mhz 
Hard DriveOptical DriveCoolingOS
Raid 0 2TB, 1.5TB Hitachi backup SONY DVD Ram + Lightscribe Hyper 212 Plus Windows 7 64bit / Zorin 
MonitorKeyboardPowerCase
LG FLATRON W2361V Saitek V.5 Cyborg Silverstone Element 750w PSU Cooler Master CM690 II Advanced 
MouseMouse PadAudioAudio
Logitech G700 NA Creative 2.1 Lenovo P950 Headset 
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My Mobile Beast
(16 items)
 
  
CPUMotherboardGraphicsRAM
I5 750 @3.809 Ghz MSI P55-GD85 XFX 5850 @ 801/1150 38c idle 8 GB Corsair XMS3 1600 Mhz 
Hard DriveOptical DriveCoolingOS
Raid 0 2TB, 1.5TB Hitachi backup SONY DVD Ram + Lightscribe Hyper 212 Plus Windows 7 64bit / Zorin 
MonitorKeyboardPowerCase
LG FLATRON W2361V Saitek V.5 Cyborg Silverstone Element 750w PSU Cooler Master CM690 II Advanced 
MouseMouse PadAudioAudio
Logitech G700 NA Creative 2.1 Lenovo P950 Headset 
  hide details  
Reply
post #3 of 3
Thread Starter 
Quote:
Originally Posted by zalittle View Post
First the MCE is a linux kernel boot error I believe. Therefore Intel would have no idea what it meant. I am in no way competent to give any Linux advice though.
Actually MCE is a CPU generated error that is saved in the CPU internal buffer. The difference is how the two O/Ss handle it. Windows will throw a BSOD while Linux might have a kernel panic depending on whether it is recoverable and you can read the error from the mcelog. What is happening in my case is an MCE followed by a kernel panic, which means that whatever happens is unrecoverable.

Quote:
If you are dead set on running Ubuntu or a variant, may I suggest Zorin 4. I run it myself and like it.
The thing is Ubuntu is my primary O/S. That's where all the work gets done. I only have Windows for games and I only need the overclock for Flight Simulator X, so it doesn't make much sense to switch out of Ubuntu because of this. Besides it looks like the problem is tied to the kernel not the specific distro and there is a very good chance that this is a hardware problem that Windows is simply ignoring.

Quote:
I also have had difficulty setting memory clocks and overclocking my I5. Try backing down the multiplier to 20, and try different settings of 195 or so and back the core voltage to under 1.3v. Be sure and raise the VTT to at least 1.28v. Also, I had to back off from 1600 Mhz on the memory to get the system stable.
Here is a link to my most stable overclock yet.http://www.flickr.com/photos/5806599...40/lightbox/#/
Isn't it better stability wise to keep the BCLK as low as possible and maximise the multiplier? Also in your pic I see that you've run Prime95 for only 5 minutes. That's not a good indication of stability. I've had Prime95 throw an error 18hrs into the test in an unstable OC. I believe 24hrs is a good rule of thumb when it comes to stress testing.
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