P6X58D-E and i7 920 - voltage offset overclocking

[andygbrown]

I am hoping someone can offer advice on a process to configure voltage offset overclocking for a P6X58D-E and i7 920?

I have had an i7 920 on an P6X58D-E for a couple of years, comfortably overclocked with a 171 x 21.0 at 1.25 volts for the CPU (1.275 QPI and 1.64 DRAM bus voltage) - nothing extreme but 100 % reliable.

I have switched it to offset CPU voltage at 0.05 V to try and reduce overall power usage (giving idle volts of 0.992 and full load of 1.256, dropping to 1.248 V). This runs stable for any length of time during stress testing using p95, but under normal use it will intermittently (within 24 hours or so) restart, or refuse to load into windows after a restart. I am guessing this is because of the voltage extremes with all cores suddenly idle or maybe a single core only under load - however this is indeed a complete guess.

So - should I now increase, or decrease the offset voltage? I am unsure exactly what "offset voltage" does (is it just the voltage dropped under stock when idle, and added to stock when under load)? Should I use LLC? Can anyone provide any links to articles that explain it thoroughly? Should I restart the overclock process and work out a stock voltage first?

My two intel 2600k rigs with Maximus IV GENE-Z are both offset overclocked successfully, but one major difference with the P6X58D-E is that it doesn't let you set negative voltages, so I am guessing the mechanisms are slightly different.

Thanks in advance...

[HiVizMan]

I would increase the offset voltage by two notches. The CPU will only use the VCore when under load.

[andygbrown]

I would increase the offset voltage by two notches. The CPU will only use the VCore when under load.

I'll try that out and report back. Unforunately I'm not near the machine at the moment, but I will have a go at the weekend. Thanks for the advice.

Does increasing the offset lead to a lower idle voltage as well as a higher load voltage, or would just shift both idle and load up by the same amount? It seems a lot more obvious on the later boards as to what it does.

Rgds ...

[HiVizMan]

The offset only increases the voltages under stress (load) so your idle will still be the Intel register values for your CPU.

[andygbrown]

I would increase the offset voltage by two notches. The CPU will only use the VCore when under load.

I tried this and it would get to the windows startup logo (before login) and then reset. I increased the voltage by 2 notches each time eventually getting up to 0.1V before I finally set all the voltages in the CPU voltage section as below. The settings were a complete guess (based roughly on the defaults). So my questions now are:

1. is there a better way of working out these voltages (is there somewhere I can find out what they do and how to work out what they should be)?
2. Should I consider enabling LLC (and if so what settings should I use)?
3. Is there a voltage offset overclocking guide anywhere I can follow instead of wasting your time ;-) ?

Thanks for your help ...

Settings are now:

CPU Voltage Control: Offset --> Offset
CPU Voltage:         0.05   --> 0.05
CPU PLL Voltage:     Auto   --> 1.80
QPI/DRAM Voltage:    1.275  --> 1.27500
IOH Voltage:         Auto   --> 1.14
IOH PCIE Voltage:    Auto   --> 1.5
ICH Voltage:         Auto   --> 1.2
ICH PCIE Voltage:    Auto   --> 1.5
DRAM Bus Voltage:    1.64   --> 1.64

[HiVizMan]

The simple formula would be to take the manual voltage value that worked before and subtract the default voltage and what you are left with is the amount of offset that you should use.

LLC I would suggest a reasonably low or medium amount of LLC.

[andygbrown]

LLC I would suggest a reasonably low or medium amount of LLC.

Thank you, if I see instability after these changes I will try a low LLC setting as per your suggestion.

The simple formula would be to take the manual voltage value that worked before and subtract the default voltage and what you are left with is the amount of offset that you should use.

I was thinking that in this case the CPU PLL, IOH and ICH voltages seem to have made the difference. Setting them to the manual values instead of auto resulted in it booting properly. Is there any guide to what to do with these?