Unstable computer after overclocking Intel Core i7 920

[Macario]

I have a computer which I have been using from almost a year now. The processor is an Intel Core i7 920 which is overclock to 4.0 GHz. Processor, video card and motherboard are water cooled. Below is my system specs:

Motherboard: Asus P6T Deluxe V2
Processor: Intel Core i7 920
Memory: 12 GB (6 x 2 GB) G. Skill DDR3-2000 Trident
Storage: 2 x 80GB Intel X25-M (RAID 0) + 2 x 1 TB Samsung Spinpoint F1 (RAID 1)
Video card: HIS ATI Radeon HD 5870
Electricity supply: Corsair HX850W
Operating system: Windows 7 Ultimate (64-bit)

The system was up until a little while ago and has been completely stable with four GHz processor (I can say that because I run Prime95 as long as I wanted, and that it never appeared on any issue that could be related to overclock). But after some time I began to get the blue screen every now and then with error code "0x0000009C: MACHINE_CHECK_EXCEPTION". After a online search I came to the conclusion that this was due to high temperatures, hardware failure or excessive overclocking. Temperatures excluded me immediately, for water cooling can not hold down to a reasonable level. So I try to clock down to the default settings, and then the problem disappeared. As such, the solution is probably simple and straightforward, and I could probably just clockwise down a bit and been well pleased with it. But I'm just a little curious about what it might be that has happened since everything has seemed 100% over such a long time. I try to run Memtest86+ for over 15 hours (8 pass) without any error indication. I can still run Prime95 for several hours without failure, and in daily use as the computer behaves fine. The last time everything has been disrupted have been in the middle of the night, when the computer just sits there. I know that such errors like this here can be almost hopeless to diagnose. So I thought to ask here to know if there is someone who has any input or experiences that could be helpful? One may well say that there has been a small "prestige questions" to get your machine stable at 4 GHz. For the settings I've used all the way to overclock my preview, see here:

BCLK: 200 MHz
Multiplier: 20x
CPU Voltage: 1.375 V
QPI / DRAM Core Voltage: 1.35 V
Intel SpeedStep: OFF

Everything else is on auto (in the moment is DRAM Bus Voltage of 1.56 V and CPU PLL to 1.80 V).

[Viceman]

Wanted in the first half, tried to write down the numbers you overclocked to. Reset the bios and check if problems are still there. Remember that when overclocking, there is no guarantee that the machine will be stable at much strain over time, might just be a RAM chip that fails. Possibly your computer is not more a 99% stable at 4 GHz, but becomes stable at 3.99 Ghz? Do not know, but you just have to try out. You should avoid putting anything on "auto" because if you overclock, you have no control on what voltage the motherboard gives out or whether the Volt is stable. It may lead to the motherboard can be unstable over time.

[.:MUNDITO:.]

I have also experienced this on the 775 platform. Overclocked a E2220 from 2.4 to 3.3 ghz and ran prime for two days without problems. Later, there appeared various problems. The machine will not start and gives the message "overclock failed". It started when I turned it off and tried again. Sometimes it was blue. Never any problem under load. I have gradually stepped down no overclock to 2.8 ghz, but I would also like to have it up again. Has not been tested so much because it is on the cabin. Had a different layout I experimented a bit with where I got a stable overclock with a Q9400 at approx. 3.6 ghz. It was tested with both Prime and OCCT. But here appeared blue and the other nonsense now and then. Never had any problems under heavy load. Here, I reduced gradually overclock to 3.4 ghz. The system had no errors during the load, even with very thorough and lengthy testing. Nevertheless appeared minor incidents, such as. "Overclock failed" at startup. But it started again just fine I hit it off and on again. All temperatures are fine by the way, always under 70 at full load. I'm left with the impression that either the processor has deteriorated as a result of no overclock, or that the motherboard is unstable. Both of these two cards I bought as a demo board, and some have wondered if it could be the cause

[Macario]

Thanks for the quick replies, guys! I have already tried to reset the BIOS and start from scratch again. The problem is still there. I am clear that there are not any guarantees when it comes to overclocking, but I have always been as careful as I can. Besides, I spent some extra money on quality components just to try to avoid that something was wrong. When it comes to voltages, mean that everything should be on manually, or just the two I mentioned above (DRAM Bus Voltage, and CPU PLL)? There is a fairly long list of voltages that can be adjusted for all the bow and sides. Symptoms you describe here heard very similar in terms of what I experienced.

[.:MUNDITO:.]

This is normal. How much it swings varies from motherboard to motherboard. On several of my cards can fluctuate much more, often depending on whether it is debit or not. The deviation is with you is very small. Probably because you have a good motherboard. It is also common that the voltage is lower than the setting in the bios. It's called vdroop as far as I remember.