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Internal PLL Overvoltage

Retired
Not applicable
Internal PLL Overvoltage should only be enabled if needed right? I am running Prime95 right now on a 4.8Ghz OC that passed with it enabled yesterday just fine. It appears to be passing today too with it disabled. A lot of people say 4.8Ghz is when you need it on. Answer?
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7 REPLIES 7

Praz
Level 13
At what multiplier PLL Overvoltage needs to be enabled is dependent on the CPU. Prime95/LinX type utilities are not the final proof of stability on this platform though. If you see instability with normal programs/games testing with PLL Overvoltage disabled would be a good first move.

Retired
Not applicable
So just keep running my test and do normal operations for a few days and see if I get a BSOD? If not leave Internal PPL Overvoltage disabled and be marry?

Praz
Level 13
Sounds like a plan. 🙂

Retired
Not applicable
Another question about Internal PLL...

Why does everyone recommend you keep it off? Is it solely for the reason when enabled, you cannot come out of sleep? Are there any other reasons?

TheGeneral
Level 7
The sleep thing is anoying, but i think its also the fact that PLL voltage can do the most harm to sandybridges if it gets too high. When compared to vcore etc. And you can run a little cooler with it lower too.

To quote Raja on his Maximus IV GENE-Z guide here - http://www.asusrog.com/forums/showthread.php?2787-Maximus-IV-GENE-Z-BIOS-Guide-Overclocking

He says this:

CPU PLL Voltage: Sets the voltage for the internal phase locked loop. The role of the PLL is to ensure that the output clock of the internal processor frequency synthesizers maintains phase coherency with the reference clock signal (supplied from a clock generator located within the PCH).

Unlike Nehalem/Gulftown architectures, Sandybridge can benefit from a small increase to PLL voltage when running higher CPU multiplier ratios (hence CPU core frequency). As always, caution is advised with regards to over-voltage on this rail – personally I don’t use any more than 1.85V and that too when processors are sub-zero cooled. Excessive PLL voltage can degrade or kill a processor quicker than overvoltage on any other voltage rail.


Id say that's pretty much all there is to know about PLL 🙂


*EDIT*

Just forgot to mention, i've run with the PLL OV on and off and it seems to never deviate from 1.8v, id only imagine because I haven't over-clocked high enough yet and 1.8v is the default as far as I know. Some peeps are running with a PLL of 1.55v just fine 🙂

Id suggest see if your OK with it off as you said, and then if you are, see how low you can take it and just stay there to get all the benefits. 🙂

I think the OV is to help those peeps who want 5GHz and cant quite make it without it.

Praz
Level 13
General, Internal PLL Overvoltage and CPU PLL Voltage are not the same thing.

TheGeneral
Level 7
Oh i see,

So your saying that the internal PLL over voltage will not affect the CPU PLL voltage at all? That is why i have not noticed it change with the setting on or off? Sorry now I understand!

So how could one monitor Internal PLL overvoltage? Any idea what the default values are? Suppose it depends on cpu. Would be nice if its possible to see it in action!