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Sandybridge : manual vs. offset voltage?

post #1 of 8
Thread Starter 
Hi, I have done a search, however could not find a thread that directly addressed my question so....

I have read that it is more beneficial to have your voltage set to offset mode rather than a manual voltage, once you have found a decent overclock.

Firstly, why is this? I understand that the main difference between manual & offset is that manual will be running the chip with that voltage the whole time, whilst offset just increases the voltage as needed, however is there anything else at work?

Secondly, how would I go about it?! I read that you can take the load voltage from Real-temp and use this as a guideline, however I wouldn't know how to turn this in to an amount to put in to my bios!

Thanks in advance, krs
post #2 of 8
Basically it's a power and slight heat saving issue. Power (P) = Voltage(V) * Current(I). The current varies proportional to the cpu load; less load = less current.

Proof:
In manual mode you have your voltage constant so in effect the power draw from your cpu is directly proportional to the current load.
P(manual)= V(manual)*I or V(manual) = P(manual)/ I
and similarly V(offset) = P(offset)/I

In offset mode the voltage can change but is always less than or equal to the manual voltage: V(offset) ≤ V(manual) plugging in the two equations above gives you:

P(offset)/I ≤ P(manual)/ I; or simply
P(offset) ≤ P(manual)

So in offset mode you will always use the same or less power. In the real word though it is always less because your cpu probably will not be at full load 24/7.

As for putting that into your bios it varies by board. I think we have the same board and for me I had to trail and error it to get the correct offset. The displayed voltage in bios did not correspond to the correct offset voltage so what I had to do was put in a offset, boot up and put the cpu under load and check the voltage. Then adjust the offset up or down and repeat until the load voltage was the same as my stable manual voltage. It is not hard to do once you know what your minimum stable manual voltage is and shouldn't take long to narrow in on it in offset mode.

Do note that sometimes when using offset mode the cpu will crash when idling also so test both before calling it stable. This happens when offset drops the idle voltage to low. If this happens just bump your voltage up one notch and you should be golden.

Hope this all helps and good luck!
post #3 of 8
These two links are gold, Munaim's Sandy Guide (post 1):

http://www.overclock.net/t/968053/official-the-sandy-stable-club-guides-voltages-temps-bios-templates-inc-spreadsheet

And for your motherboard in particular (link also found in Munaim's Guide):

http://hardforum.com/showthread.php?t=1578110

The Asus one will tell you exactly how offset/fixed will affect your system, and how to set up your bios to start overclocking, it also includes term definitions etc smile.gif

Another good one is here, again for Asus:

http://rog.asus.com/forum/showthread.php?2453-P67-Z68-BIOS-Guide-BASIC-Intermediate-Overclocking
Edited by BabyModR - 5/1/12 at 6:19pm
    
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post #4 of 8
I prefer or love offset on overclocked SB over 4.5Ghz which most of SB owners run ...think about it this way- how much is your rig under constant load ,if your answer is more than 50% of your daily use than fixed should be the way if all you do is game ,browse the internet and some other light~medium stuff (which will come down to 20~35%) this will make the idea of pumping all that voltage through your chip unnecessary to say the list
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post #5 of 8
Thread Starter 
thanks for all your replies biggrin.gif my computer certainly doesn't run 100% much of the time as I mostly use it for gaming / browsing...it's just that it's taken me some time to achieve a stable overclock at 5 GHz and I don't want to do anything that's going to mess it up!!!
post #6 of 8
why in the world would you want to run 5.0 on daily bases with single GPU is beyond me wth.gif and BTW you won't mess up anything ,just save your profile in bios
    
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post #7 of 8
Offset is better..When I use offset..It lowers my res temp by about 5c :yessir.gif:
You can find out what your chip needs using manual..then switch to offset..just a few reboots..see what the voltage is..etc...
 
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post #8 of 8
Thread Starter 
...cheers...had a look at that RoG guide that was linked and tried switching to offset mode...coming back into windows, offset had set core voltage to 1.624 V eek.gif whilst CPU-Z was previously giving me a core voltage of 1.504 V under load...however going back in to bios to set the -ve offset to 0.120 resulted in my computer not being able to boot into Windows mad.gif
Quote:
Originally Posted by coolhandluke41 View Post

why in the world would you want to run 5.0 on daily bases with single GPU is beyond me

mad.gif because I don't have enough lanes for dual GPU?
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