Can someone help me explain this strange overclocking behaviour?...(i5-750)

[joxang]

Hey all,

Hope someone can help me with these characteristics but I am baffled.

Have been running my i5 750 with the specs in my sig at 4ghz (20x200) with 20 runs Linx stable (with the newest linpack) and a couple hours of prime. This is normally good enough for me as I do not do anything that stressful and I haven't had any problems since using this overclock a few months ago.

Since last week I have been trying to get it stable at 3.8ghz as it was quite warm. Did get it stable but when using the Dynamic Vid feature on my Gigabyte board however, it enters an infinite loop when exiting sleep and I have to clear the cmos to get it to boot. So I tried different multipliers to see if it behaved any better, as I heard that these chips prefer odd ones, and I cannot even get to the bios screen without having to recover the bios. Any ideas on what could be causing this behaviour would be appreciated, as I remember when I did try 3.8ghz when I just got the chip with the combinations listed below they were fine.

4ghz (21x191) Vcore: 1.33V, Qpi/Vtt: 1.26V, PCH: 1.1V
Stable using the method above

4ghz (20x200) Vcore: 1.33V, Qpi/Vtt: 1.26V, PCH: 1.1V
Stable using the method above

3.8ghz (21x181) Vcore: 1.26V - 1.33V, Qpi/Vtt: 1.26V, PCH: 1.1V
Cannot get to bios

3.8ghz (20x190) Vcore: 1.26V - 1.33V, Qpi/Vtt: 1.26V, PCH: 1.1V
Cannot get to bios

3.8ghz (19x200) Vcore: 1.26V, Qpi/Vtt: 1.24V, PCH: 1.1V
Using Dynamic Vid stable with the method above but goes into an infinite loop when exiting sleep

3.8ghz (19x200) Vcore: 1.26V, Qpi/Vtt: 1.24V, PCH: 1.1V
Is stable with no Dynamic Vid

I could just run 19x200 without Dynamic Vid as the Vid probably drops too low to get the chip to boot but I would like to know if possible why my chip behaves as it does.

Thanks

 

[lehmann]

turn off dynamic vid. im also pretty sure if you gave that rig a good stress test you will find your vcore to low. all of mine need 1.38 or more @4.0 thats a i5-750, 860,875k

 

[sirmonkey1985]

usually dynamic VID setups are based on highest voltage setting which determines what your lowest voltage setting will be. so try setting the voltage high, say 1.3v @ 3.8Ghz see if you can get it to boot.. then try going lower or higher and see what happens..

 

[Genny]

I doubt I'd even be able to post with 4 ghz @ 1.33v. The minimum I've found to even be remotely stable is 1.36v...granted all are a bit different.