i7 920, worker stop but it never happened before..
 

Please excuse me if this was asked before, I'm very confused right now...

So, my i7 920 @3.4ghz has passed 3 hours of In-place FFT testing before and been running fine with gaming and encoding video for about month. But today, I tried to overclock it to 4 ghz but didn't succeed and had to return to 3.4 ghz. I tortured with In-place FFT again and for the first time, noticed that some workers stopped after about 20' minutes of the test resulting to cpu usage and temp reduced. I thought that the meaning of this is that core was unstable. But how could it be unstable if it has passed this test and everything (environment temp, setting) were the same (except for the vcore in cpu-z, sometime went to 1.208 instead of 1.200 as before, in bios it was set to 1.20000 v, though )?

Pls give me some advice or explanation....

Cpu-z:

[url]http://img241.imageshack.us/img241/6534/814200941618am.gif[/url]
[url]http://img263.imageshack.us/img263/5889/814200941738am.gif[/url]

My system:
Mobo: Asus P6T SE
Cooler: Thermalright Ultra 120 Extreme
Ram: 3x2GB OCZ Plantinum 1600 cl 7-7-7-24 (oced to 1700 @ 7-7-7-24)
PSU: Antec TruePower Quattro 850
VGA: Asus GTX295
HDD: 320GB 8Mb cache WD blue caviar

[QUOTE=ih2try;185357]
So, my i7 920 @3.4ghz has passed 3 hours of In-place FFT testing before and been running fine with gaming and encoding video for about month. But today, I tried to overclock it to 4 ghz but didn't succeed and had to return to 3.4 ghz. I tortured with In-place FFT again and for the first time, noticed that some workers stopped after about 20' minutes of the test resulting to cpu usage and temp reduced. I thought that the meaning of this is that core was unstable. But how could it be unstable if it has passed this test and everything (environment temp, setting) were the same (except for the vcore in cpu-z, sometime went to 1.208 instead of 1.200 as before, in bios it was set to 1.20000 v, though )?
[/QUOTE]

Your experiment to 4 GHz may have caused some permanent harm.

I'm surprised you could run 3.4GHz at 1.2V to begin with, that's pretty low. I would expect 1.3V to be nearer the stable voltage.