Intel Burn Test seems to be more tolerant of under-voltage and excessive Vdroop than Prime95. I believe that is because IBT simply Linpacks your CPU into an ultra-high load state and holds it there with little power transients but Prime95 Blend has constant power transients as FFT lengths change asynchronously. Due to Prime95 Blend's constantly changing FFT lengths, you encounter many more load/unload transients and expose instability that is not commonly caught with IBT. My Prime95 Blend stable voltages are consistently 0.010 to 0.020 higher than IBT "stable" initial values.
Originally Posted by HornetMaX
Originally Posted by shad0wfax I hid my own quote in a spoiler. (Click to show)
1.368 Vcore is a perfectly fine voltage for the 2500K. The "safe" 24/7 "user limit" most people believe in is around 1.410 Vcore or 1.420 Vcore.
You can bump the current capability up to 140% and you'll get much more performance out of your OC in terms of flop/s and, in theory, you won't have to change any other settings. (It just removes some throttles that are safe to remove and are holding back your CPU.) I have my current capability at 140% even when I'm at 4.9 GHz and 1.406 Vcore. It's also normally best to put Phase Control to Extreme and VRM frequency to Manual 350. This would probably solve your blue-screen problems and allow you to get a higher OC frequency with the same settings or else use a lower Vcore with the same OC frequency.
My VID at 4.7 GHz and 100% load on all cores is considerably higher than your VID and yet I'm at a lower voltage than you and stable at a higher frequency. Again, my guess is that there's plenty more room in your OC if you try out the above tweaks.
Thanks shad0wfax fro the help !
First, my 4.5GHz @ 1.340V manual Vcore BSODed me after 15min gaming (cod4). on the bright side, the automatic 4.3GHz setting (1.328V vcore, offset mode, set to auto) allowed me to play fine 3+ hours.
So I'll go with your suggestion tonight: 140% current, Phase control Extreme, VRM frequency 350 manual.
Should I also set Duty Control extreme, LLC medium and Spread spectrum disabled (seen in your BIOS settings) ?
I'm a bit confused about the Vcore offset mode setting: with the auto-OC it is now in offset mode, but the offset value is "auto".
What does this mean ? Supposing this setting is stable, how do I compute the equivalent value of offset assuming I want to get rid of the "auto" setting ?
Or should i just forget about the offset mode at the moment, make it stable, let's say, at 4.5GHz @ 1.340V manual and try to reduce the Vcore from there in manual mode ?
The 140% current, extreme phase control, and manual VRM at 350 should get you all the way to 5.0 GHz, assuming the rest of your system can handle that frequency, should you ever decide to push that far.
I also use the Duty Control Extreme and recommend that as well.
LLC Medium is a value that I came up with on my own. Using this value requires more positive offset (or less negative offset) and/or more turbo voltage additions, but results in less power being consumed by the VRM circuitry as well as the CPU itself in most situations. I discovered that a high turbo boost (or high offset) voltage along with a relatively low LLC at 4.7 GHz gave me higher benchmarks and more Flop/s than a High or Ultra High LLC with a much lower offset (or turbo boost) gave me. I discovered that on High or Ultra-High I would hit silent throttle limits and it would harm long-term benchmark performance. This is something you'll have to experiment with on a case-by-case basis and note that my rationale for using this value was based entirely on Flop/s benchmark performance to minimize throttling.
Spread Spectrum disabled is also something that you have to experiment with on a case-by-case basis. Always disable it or enable it; never let it use automatic mode. Many users have reported that enabling it is the key to reaching 4.8 - 5.2+ GHz clock speeds and that with Spread Spectrum disabled the higher clocks were not attainable. I have seen no difference with it enabled or disabled in terms of my system stability, so I disabled it, as it's one less load on the motherboard that way.
Originally Posted by zerozed
Sorry if my question is noobish. I OCed my CPU @ 4.5GHZ with manual vcore 1.28, so far stable with prime. But it constantly runs with this vcore even when speedstep is enabled and automatically underclocks itself @ 1.6GHz. Am I missing something?
Speedstep being enabled is what allows the CPU to clock itself automatically between 1.6 GHz and your 4.5 GHz setting, depending on CPU load. This is normal behavior.
Since you chose a manual voltage, your voltage will always be the vcore that you set of 1.280. If you use an offset value, then the voltage will be automatic and will vary with load. The higher the offset, the higher voltage will be, and you adjust the offset so that your peak voltage is where you desire it to be for stability. However, too high of an offset will cause your idle voltage to remain high. You could instead use a smaller positive (or even a negative) offset and then use a turbo boost voltage (which is always positive) to force your minimum voltage at idle to the lowest stable value that you desire while still maintaining the highest voltage as the minimum stable voltage at load.
Your other option is to keep your current manual settings at 1.280V 24/7 and not save as much power.
Originally Posted by am dew1
Originally Posted by MooMoo
Thats completly normal, its that function which name I just forgot
You can get your volts down with that idle 1.6GHz by using offset voltage instead of manual voltage.
I have a similar situation in that I set the manual vcore to 1.28v. What would be a good starting point using offset voltage instead?
That depends on your LLC value, and what your other BIOS settings are. Guessing without knowing the rest of your system details would not be wise. You can look at the BIOS settings I posted above to get an idea. Note that a positive offset of 0.045 resulted in the same peak voltages and stable load voltages for me as the negative offset of 0.030 combined with the turbo boost of 0.124. The negative offset with turbo boost voltage simply shifted the minimum voltage from 1.000V down to 0.920V. (I do not get bluescreens at idle, but some may if their Vcore drops this low.)
Edited by shad0wfax - 2/15/12 at 3:27am