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Undervolting Sandy Bridge CPUs - i7 2600k, etc

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Bluescreendeath

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Discussion starter · #1 ·
Anyone undervolt at stock or undervolt + overclock their Sandy Bridge?

What is the lowest stable voltage they got with their Sandy Bridge (especially i5 2500/2500k, i7 2600/2600k, 2700, etc).

I'm currently experimenting with undervolting my i7 2600k. I've had it at 1.05v stable at Prime95 FFT for 6+ hours. Currently running it at 1.025v (goes down to 1.008v at load) with Prime95 FFT at 3 hours and counting. Is this normal?

What has other folks here got with their Sandy Bridge undervolting?
 
#2 ·
I've got my 3820 to 1.17v at 4.3GHz, which is an under volt and an overclock on the stock 1.23v

So the answer is yes, I'm sure you might be able to go under 1v if your chip is of very good quality. What clock speed are you at?
 
#4 ·
50 passes of IBT and 20 mins of P95 is enough to "assume" its stable and try to lower it further. For a finaltest, 100 passes of IBT on the highest and 4+ hours of P95 is sufficient.
 
Discussion starter · #7 ·
So far, I'm Prime95 Small FFT stable for 3+ hours with voltage at 1.020v-1.025v - with v drop, it goes down to 1.008v at load. When I drop it down to 1.010v (which goes below 1.0v with v drop at load), Prime95 picks up errors in core #2, and the PC crashes within an hour.
 
Discussion starter · #9 ·
I brought voltage down to 1.015v, ran Prime95 and watched vdroop go down to an amazing flat 1.000v - wooot!
biggrin.gif
Then it crashed about 30 minutes later.
frown.gif


I guess 1.020v is the lowest I can go at stock settings....or so I thought. I ran it again with Prime95, and after a few hours, core #2 started having problems and had 1 error. Time to bring up the voltage again I suppose...
 
#12 ·
I was able to get mine down to 0.98v 24 hour P95 stable when it was brand new, doubtful it could happen now after 5 years of use though.

As for overclock + undervolt, stock voltage only got me up to 4.4 Ghz so that was a complete non starter.
 
#13 ·
I now thread is old, but i still have this chip
I have a 2600 non k on an asus z77 extreme3, i was able to bring down my voltage quite a bit (0.92V@load) using voltage offset and slightly under-clocking. im running at 2700mhz turbo boost instead of 3200mhz. its running at ~85% of its original performance but much cooler. shaved down about 5-6 celcious at idle. Also, running prime and aida64 stress test my max temp was 55c at 450RPMS!! dead silent now.

undervoltsettings.png 285k .png file
 

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Discussion starter · #15 ·
Quote:
Originally Posted by gabrielpe View Post

I now thread is old, but i still have this chip
I have a 2600 non k on an asus z77 extreme3, i was able to bring down my voltage quite a bit (0.92V@load) using voltage offset and slightly under-clocking. im running at 2700mhz turbo boost instead of 3200mhz. its running at ~85% of its original performance but much cooler. shaved down about 5-6 celcious at idle. Also, running prime and aida64 stress test my max temp was 55c at 450RPMS!! dead silent now.

undervoltsettings.png 285k .png file
Click to expand...
Very nice! I currently have my i7 2600k chip overclocked to 4.0GHz with 1.165v (had it originally at 1.155v for a year, then bumped it to 1.160 for another year, then to 1.165v due to crashes)

I have a Cooler Master CM N520 heatsink/cooler, with fans running at a near silent 35% at regular use, and my temperatures maxes out at 65'C during intensive gaming (95% CPU usage in Warhammer Vermintide) - fans stay at 35% during gaming as my target temp is set to 70'C.
 
#16 ·
Cool man, my overclock is not finished yet though, right now its running 100% stable but I want to slowly bring the frequency as high as i can by changing other voltages. right now i don't notice much of a difference compared to when it was stock, except its way cooler now since before it was pushing like ~1.2v on auto voltage setting.

These are my volts in idle.
Do you use hyper-threading for regular browsing and gaming or do you turn it off if you aren't folding, coding, or video editing? I'd like to know your opinion in that.

https://postimg.org/image/xy767k8dx/photo hosting sites
 
Discussion starter · #17 ·
Quote:
Originally Posted by gabrielpe View Post

Cool man, my overclock is not finished yet though, right now its running 100% stable but I want to slowly bring the frequency as high as i can by changing other voltages. right now i don't notice much of a difference compared to when it was stock, except its way cooler now since before it was pushing like ~1.2v on auto voltage setting.

These are my volts in idle.
Do you use hyper-threading for regular browsing and gaming or do you turn it off if you aren't folding, coding, or video editing? I'd like to know your opinion in that.

https://postimg.org/image/xy767k8dx/photo hosting sites
Click to expand...
I currently have my volts at a constant 1.165v. I have no idea how to get it to downvolt when idle with my motherboard options.

I use hyperthreading for everything - a lot of games can make use of more than 4 threads and HT keeps the 2600k relevant. It's also great for mulitasking (eg. running virus scans in the background). If you take a look at gaming benchmarks from Techspot, the i5-2500k (basically a 2600k without hyperthreading) falls behind in a lot of games and applications because it lacks hyperthreading. The i7-2600k is still relevant thanks to hyper threading.

I do have turbo boost disabled since it makes my clocks at my current voltage unstable.
 
#18 ·
Quote:
Originally Posted by Bluescreendeath View Post

I currently have my volts at a constant 1.165v. I have no idea how to get it to downvolt when idle with my motherboard options.

I use hyperthreading for everything

I do have turbo boost disabled since it makes my clocks at my current voltage unstable.
Click to expand...
thanks for your input in hyper-threading, it just didn't make sense to turn that off for performing slightly better when running single core applications.

To not run at a constant voltage=V, I'm using the offset option in my motherboard instead of selecting a specific V# like a lot overclockers do. For example, when you use auto V, the V provided is 100%stable, but at quite higher volts to keep the processor overfed. however, this allows the V to switch from idle to full throttle at specific ratios.
Offset lets you keep the "auto setting" capabilities of V fluctuation from idle to stock keeping "stock" V ratios. This setting lets you add+ or withdraw- V in increments of .005mv. right now I'm running an offset of about -.200v.

I would suggest trying to run turboboost=TB and find a voltage that will work stable if your motherboard has an offset V option for adding voltage only when TB is active. Today I had the chance to toy around with my system again and I've got 100% stable 3Ghz and running .976v@load instead of 2.7Ghz at .920v, didn't really saw any temperatures change nor an increase in fan speed for an extra 300mgz
thumb.gif
My idle voltages remained ~.005v to my previous V, but my V at load increased by adding about .008V to the processor when TB kicks in (@load).

undervoltload3.0ghz.png 149k .png file


using these offset settings is tricky, but if your mobo has them, you might be able to overclock to same speed and under-volt as well (at least when in idle with TB on). I'll keep you updated if i reach higher stable clocks while keeping a reasonably low V
cheers.gif
sorry for long
typer.gif
reply lol
 

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Discussion starter · #19 ·
Quote:
Originally Posted by gabrielpe View Post

thanks for your input in hyper-threading, it just didn't make sense to turn that off for performing slightly better when running single core applications.

To not run at a constant voltage=V, I'm using the offset option in my motherboard instead of selecting a specific V# like a lot overclockers do. For example, when you use auto V, the V provided is 100%stable, but at quite higher volts to keep the processor overfed. however, this allows the V to switch from idle to full throttle at specific ratios.
Offset lets you keep the "auto setting" capabilities of V fluctuation from idle to stock keeping "stock" V ratios. This setting lets you add+ or withdraw- V in increments of .005mv. right now I'm running an offset of about -.200v.

I would suggest trying to run turboboost=TB and find a voltage that will work stable if your motherboard has an offset V option for adding voltage only when TB is active. Today I had the chance to toy around with my system again and I've got 100% stable 3Ghz and running .976v@load instead of 2.7Ghz at .920v, didn't really saw any temperatures change nor an increase in fan speed for an extra 300mgz
thumb.gif
My idle voltages remained ~.005v to my previous V, but my V at load increased by adding about .008V to the processor when TB kicks in (@load).

undervoltload3.0ghz.png 149k .png file


using these offset settings is tricky, but if your mobo has them, you might be able to overclock to same speed and under-volt as well (at least when in idle with TB on). I'll keep you updated if i reach higher stable clocks while keeping a reasonably low V
cheers.gif
sorry for long
typer.gif
reply lol
Click to expand...
My motherboard is the MSI P67A-C45. Unfortunately, it doesn't have options for voltage offset...or I didn't see one in the last 3 years of playing with it. I think the mobo's software overclock might allow different voltages for OC, but idk..

Folks usually turn turbo boost off to increase stability. The problem with turbo is that different cores may require different voltages to get stable - the voltage has to be sufficient for the worst perform/least stable core. So to get a turbo boost speed, you may have to have a voltage higher than what is required for base blocks, and end up with a voltage high enough to get all cores to run at that speed as a base anyways.

eg.
1) 1.2v to run 4Ghz on 4 cores
2) 1.3v to run 4Ghz on 4 cores + turbo to 4.5Ghz b/c 1 or 2 cores need that much voltage to avoid instability
3) 1.3v to run 4.5Ghz on all 4 cores
---> might as well set it to 1.3v and run 4.5Ghz as a base clock and turn off turbo boost
 
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Bluescreendeath
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