How do I Undervolt the i7-6700k properly?

[Zynchro]

Hi...

I want to undervolt my i7-6700k 4.2GHz. How do I do that properly, without damaging the CPU and the rest of the hardware?

I want to undervolt my CPU to get a cooler and cheaper system. ([strike]My electricity bills are too big![/strike])

I don't know that much about overclocking and undervolting, but I do know where to find it in my BIOS settings. My motherboard is Maximus VIII Ranger. I also know that I am going to change the CPU Core Voltage. I've tried to manually enter another amount of volt. The default volt is 1.408 volt whilst on heavy load, and I want to lower it a bit. I'd be happy if i could reach 1.200 volt or 1.180 volt, but my system seems to crash when I'm going under 1.220 volt. Sometimes it reaches 1.180 without any problems at all.

I'll stay away from Manual Voltage Mode, because it only stays in the given Voltage, for example: if I change it to 1.200 volt, it stays at 1.2 and doesn't go under 1.2 .

The Adaptive and Offset modes seems out of control, because they'll never use the given voltage. I tried using the Adaptive voltage mode and I set the Addtional max turbo voltage to 1.220 volt and sometimes it moved all the way up to 1.39 volt or even 1.4 volt.

I also have one more problem with my CPU...

Whilst my CPU is idle, it goes down to 800MHz and then all the way up to 4200MHz, the exact same weird thing happens to my CPU voltage. It goes from around 0.760 volt all the way up to 1.408 volt. Is that normal for a CPU to change so often like that?

Thanks in advance!

 

[chemmajorp53]

Not to stifle your dreams, but undervolting your CPU is going to have pretty much 0 impact on your electricity bill, and by 0 I mean less than $1 a month. If you actually want your bill to be lower, I'd look at opening the fridge less often and turning down the AC a bit.

 

[Snipergod87]

Underclocking your CPU really wont make any difference in your electrical bill, you would see a larger difference turning off your screen for a few minutes a day to be honest.

And yes it is normal to have to CPU bounce between 800Mhz and 4.2Ghz with that voltage range, that is Intel's (and Windows) build in power saving technology.

 

[Zynchro]

Underclocking your CPU really wont make any difference in your electrical bill, you would see a larger difference turning off your screen for a few minutes a day to be honest.

And yes it is normal to have to CPU bounce between 800Mhz and 4.2Ghz with that voltage range, that is Intel's (and Windows) build in power saving technology.

Yeah alright... please forget all about the electricity bill thingy... do you know how I undervolt my CPU anyways?

 

[Snipergod87]

Undervolting the CPU may not work (usually Intel bins them right at the voltage needed).
You don't want a manual voltage as that wont help when the CPU goes idle, you will want a negative offset voltage instead, which may not be stable at all the speeds the CPU will jump to between 800Mhz and 4.2Ghz.
Best to start small and stress test at various CPU frequencies to test if it is stable.

If you use your computer for gaming you would see a bigger power drop by underclocking your GPU.

Other options would be to turn off or put your computer to sleep or hibernate when not using it.

 

[Ravi Sankar]

Yes but it depends on your mobo bios options as well as your cpu should be unlocked

 

[Zynchro]

Undervolting the CPU may not work (usually Intel Bins them right at the voltage needed).
You dont want a manual voltage as that wont help when the CPU goes idle, you will want a negative offset voltage instead, which may not be stable at all the speeds the CPU will jump to between 800Mhz and 4.2Ghz.
Best to start small and stress test at various CPU frequencies to test if it is stable.

Which Voltage mode should I be using? Adaptive or Offset?

 

[Snipergod87]

Offset is usually would I would use, and you will need to use a negative offset.
Adaptive will increase voltage for overclocking

 

[Zynchro]

Offset is usually would I would use, and you will need to use a negative offset.
Adaptive will increase voltage for overclocking

Yeah okay, but that was exactly what I did earlier today. I changed CPU Core Voltage Offset to -0.160 .

...i ran a 2 Hour OCCT CPU stress test only to see my CPU's Voltage go all the way up to 1.460 volt.

1.4 volt Is way more than i like!

 

[Snipergod87]

Thats very very odd a negative offset should not be increasing the voltage. I wonder if an updated BIOS would fix that. Also 1.46 is way to high in general. (I did say small incriments)

 

[Zynchro]

Thats very very odd a negative offset should not be increasing the voltage. I wonder if an updated BIOS would fix that. Also 1.46 is way to high in general. (I did say small incriments)

It's pretty strange tbh...

I think it's working now. I reset everything in BIOS and started all over again. The voltage seems to stay around 1.28v now! Sometimes it goes up to 1.31v.

Do you possibly know how I could decrease the cost of my electricity... I’ve set my monitors brightness to 50% instead of 100%, are there anything else i could do within my PC to decrease my electricity bill?

 

[mahanddeem]

OP look,
First you need to find the max voltage your CPU is being under your usual loads, I don't ever consider Prime 95 or these dangerous apps a realistic load. Let's say gaming is your usual load. Note down your max CPU vcore when you play a heavy cpu bound game.
Next go to your BIOS, switch your cpu voltage mode to manual and put something realistic(don't be too ambitious now) let's say use 1.25v and save changes.
Use your pc normally, game work anything and Observe. Run 3DMark Firestrike and Cinebench R15 and see if it works fine and no crashes.
If everything is stable let's say for few pc usage sessions, go to BIOS and reduce the voltage now to 1.240.
Rinse and repeat to see what is the manual voltage your system is unstable at when full load. Then one voltage step, let's say 0.010v is your lowest possible cpu volts under max load.
Finally use that value and put it in adaptive voltage setting in BIOS. The only problem is when your lowest stable voltage is LOWER than VID(what CPU thinks is a good voltage for the frequency), But I think this doesn't well apply to you as your CPU doesn't seem to require low voltage.

 

[Zynchro]

OP look,
First you need to find the max voltage your CPU is being under your usual loads, I don't ever consider Prime 95 or these dangerous apps a realistic load. Let's say gaming is your usual load. Note down your max CPU vcore when you play a heavy cpu bound game.
Next go to your BIOS, switch your cpu voltage mode to manual and put something realistic(don't be too ambitious now) let's say use 1.25v and save changes.
Use your pc normally, game work anything and Observe. Run 3DMark Firestrike and Cinebench R15 and see if it works fine and no crashes.
If everything is stable let's say for few pc usage sessions, go to BIOS and reduce the voltage now to 1.240.
Rinse and repeat to see what is the manual voltage your system is unstable at when full load. Then one voltage step, let's say 0.010v is your lowest possible cpu volts under max load.
Finally use that value and put it in adaptive voltage setting in BIOS. The only problem is when your lowest stable voltage is LOWER than VID(what CPU thinks is a good voltage for the frequency), But I think this doesn't well apply to you as your CPU doesn't seem to require low voltage.

Thank you for your time and effort put into explaining this.

I actually found out a fix a couple of hours ago, and it's working pretty darn good! I switched to Offset voltage mode in BIOS, and set it to Negative (-) offset, and then i applied 0.160 volt to the Negative offset! It works now! The highest voltage i'm able to achieve is 1.28 volt, which suits me just fine.

Thanks again!

 

[mahanddeem]

Glad I was of help. Big offset yes hopefully it'll not mess up with your idle voltage(it'll be maybe around 0.600v?). But keep monitoring your stability. If you observe any instability lower the offset value a hair of voltage.

 

[Zynchro]

Glad I was of help. Big offset yes hopefully it'll not mess up with your idle voltage(it'll be maybe around 0.600v?). But keep monitoring your stability. If you observe any instability lower the offset value a hair of voltage.

Yeah okay thank you, i'll keep an eye out for system instability. 😉