I finally figured out why my overclocks on my current main rig is unstable...

[Randall Leong]

Originally Posted by Rod Sandage

Do you have turbo, TM Load or C1E enabled these allow the processor to throttle up and down for load. I do have them enabled (processor runs slower at idle and low loads) but have read that it can cause problems. You may try disabling these they may be called something different in your bios. This locks the processor at one speed (multiplier) continouesly

Turbo was disabled but EIST and C1E were enabled when I started experiencing the occasional BSOD problem. I had it stable when EIST and C1E were disabled.

Nonetheless, I just disabled it, and set the VTT to 1.335V.

And had I stuck with the 920 instead of going with the 950, I would have had a difficult time getting things stable at even 3.8GHz: Neither my GA-X58A-UD3R nor my backup DX58SO allows me to set a 21x multiplier with the 920 unless I have both EIST and Turbo on (well, the X58A-UD3R allows me to enter 21x, but the BIOS will revert to 20x unless both EIST and Turbo are enabled). The DX58SO won't allow me to even manually set 21x at all with the 920; the 21x multiplier is automatically enabled if I enable both EIST and Turbo.

[Rod Sandage]

Well you might have to step back to 3.8 and be stable and not have to worry about the problems to run higher, not to say it cant be done but is it worth the small difference to you. It is kinda like building race car motors to get the last 50 horse power comes at a price many times it takes to get the first 50. I think computers are the same, high peformance motherboards, coolers ect. all come at a price to get the last little bit of performance. I had my system up to 4.5 for a short time and decided the stress on the system for what I used it for wasn't worth it. Besides if I fried a 980x I would be without a new computer again for a long time.
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[Randall Leong]

So far so good at my system's new settings. It was the CPU's power-saving settings that so far caused the instability.

Unfortunately, I have the first revision of the Gigabyte GA-X58A-UD3R motherboard, which has only 8-phase power. The second revision of that same board now has 12-phase power.

[Randall Leong]

Originally Posted by Randall Leong

Occasionally, the system locks up at the "Starting Windows" screen, and also get an occasional BSOD (Black Screen Of Death).

An update on the lock-ups and data corruption black screens:

It occasionally did this at even stock speeds. And even when I locked the CPU core speed down to a bare minimum 1.6GHz (133 x 12), the system still locked up on boot and occasionally black screened while in Windows.

I tried everything, and found the culprit: My boot hard drive (non-RAID). This is a Samsung F3 1TB hard drive with firmware version 1AJ10002, which has CCTL (Samsung's and Hitachi's equivalent to Western Digital's TLER and Seagate's ERC) enabled by default and set to 7.5 seconds for both read and write. These defaults make the drive better-suited to true RAIDs like RAID 5 or RAID 10 but actually degrade performance and stability in non-RAID or RAID 0 use. Unfortunately, there is no permanent solution to this short of replacing the drive - but I started using a third-party CCTL utility as a temporary fix. I disabled CCTL altogether in that drive, and the new settings held during a warm reboot - but then, if I turned the computer off, the CCTL settings would reset to the default "Enabled, 7.5 seconds". During the first half of 2010, Samsung saved themselves money by simply carrying over a firmware version intended for the similar SpinPoint F3R series HE103SJ drive (the desktop version is the HD103SJ) to the F3 series. The two drives with the 1AJ10001 firmware are actually newer than the drive with the 1AJ10002 firmware, based on their date of manufacture.

The other two 1TB Samsung F3's that I have in my main rig have the correct firmware, 1AJ10001, which have CCTL supported but disabled by default. This setting is more appropriate for JBOD and RAID 0 use.