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offset vs manual vcore - power consumption

post #1 of 10
Thread Starter 
Hello,

I'm trying to figure out how big disadvantage it is to have vcore set manually instead of using offset in terms of power consumption. Motherboard can undervolt the cpu in idle only with offset setting as all of you know. Since my pc runs most of a day, even a 10-20W savings in IDLE can be seen on my bill after several years (I don't upgrade pc that often and prefer to spend the money for better build instead of donating electricity company).

So does anybody have the exact numbers (for Ivy in the best case)? I was not able to google anything solid.

Thank you.
post #2 of 10
Thread Starter 
Nobody? The thing is I'm choosing between MSI and the other manufacturers. I would pick Gigabyte or Asus right away but their mosfet (no)heatsinks make me sick. MSI is really much better in this. But you can not set the offset vcore...
post #3 of 10
Ill weigh in lol. I prefer an offset voltage always. And yeah the MSI boards i would stear clear of esp for that reasona dn get an Asus or Giga board.
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post #4 of 10
I am a big fan of using a fixed core voltage combined with the C3/C6 sleep states. This is all you have to do to minimize power consumption and you also end up with great performance too without having to fool around with setting just the right offset voltage.

idlecores.png

The screen shot is from a Core i5-3570K running somewhere around 4000 MHz to 4200 MHz. My individual cores are able to spend over 99% of the time in the C6 sleep state. In my original testing, putting the entire CPU package into the deeper sleep states was not resulting in any power savings at the wall so I turned those off. That might have been due to an early bios issue so I plan to retest that in the near future.

The voltage reported by CPU-Z, etc. when a CPU is in the C6 sleep state becomes irrelevant so there is no downside to using a fixed voltage. It makes it a lot easier to dial in a quick overclock and when idle, over 99% of the time this CPU is running at close to 0 volts because the cores are in C6.

Ivy Bridge works great and Intel has made some big improvements to how fast a CPU core can transition from C6 back to the full power C0 state. You are far better off setting your CPU up like this than trying to save power by disabling these sleep states and then forcing your CPU to use a low multiplier when idle. All that does is it uses more power and reduces off idle responsiveness.

Putting a CPU core to sleep is the best way to save power. When using the Intel GPU and overclocked to 4200 MHz, an entire computer can draw as little as 35 Watts from the wall at idle when set up correctly. Buy a Kill-a-Watt meter and use the latest version of RealTemp to dial in your sleep states. I will try to post some more results and power consumption numbers when I get the chance.

RealTemp T|I Edition
http://www.overclock.net/t/1330144/realtemp-t-i-edition

I recommend the Windows High Performance profile. When you have C6 enabled, you are better off letting the CPU manage itself. Ivy Bridge does a far better job than Windows when maximizing performance and minimizing power consumption. Cores that are spending most of their time asleep also run nice and cool at idle, even when using the crappy OEM heatsink.

http://img266.imageshack.us/img266/8822/c6sleep.png
Edited by unclewebb - 2/2/13 at 9:38am
post #5 of 10
Thread Starter 
Clexzor: you have 3570k @ 4.9 Ghz using 1.408v on MB with no mosfet heatsink, wow smile.gif

unclewebb: that is very interesting idea. I believe many overclockers do not use c3/c6 states because of system instability. If the oced system is stable, than it indeed looks like better way than using EIST for underclocking and undervolting.
post #6 of 10
I think C3 / C6 get blamed for a lot of instability when it's the offset voltages that are causing the problem. First crash, C3 and C6 automatically get disabled and never get turned on again.

On a stable CPU, the cores should be able to use C3 / C6 without crashing.
post #7 of 10
Quote:
Originally Posted by unclewebb View Post

I think C3 / C6 get blamed for a lot of instability when it's the offset voltages that are causing the problem.

Do you think it is caused by what the user has set or the hardware implementation?
post #8 of 10
Quote:
Originally Posted by unclewebb View Post

I think C3 / C6 get blamed for a lot of instability when it's the offset voltages that are causing the problem. First crash, C3 and C6 automatically get disabled and never get turned on again.

On a stable CPU, the cores should be able to use C3 / C6 without crashing.

Quote:
Originally Posted by ucode View Post

Do you think it is caused by what the user has set or the hardware implementation?

if offset is implemented the right way, there should be no problem,
if you run into problems using offset,
your fixed vcore prolly wasnt stable either to start with i think,
at least i never had a problem, and i always use offset with my oc's,
upto 4.8ghz, where i use a 0.160V offset..

C3, C6. This is a deeper sleep with a complete core(s) shut down (Gate off) and no voltage/Data at all.
harder to recover from quickly, previous data is cached elsewhere and needs to be re-cached in L3 memory
to re initialize full muliticore, multithread use. Part of Core parking
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post #9 of 10
Thanks for the reply VonDutch. The reason I asked Kevin is because in the early days of SNB there use to be a peculiarity when setting C3/C6 where things like VID and VDroop would seem to change. BTW maybe you made a typo with L3, AFAIK L3 is only flushed / reduced with C7 package state which is for mobile chips, not DT.

Carlos1, not sure what you want but options are offset, additional turbo voltage and fixed.

Offset itself is static and will help reduce voltages or increase them. If you are trying to undervolt for lower power this may be your best option but as Kevin (UW) pointed out the difference may not be that great depending on what you are doing.

Additional turbo voltage is dynamic but only works with turbo multi's to give a positive increase. You may possibly be able to use this if offset is not available on the MB for voltages up to 1.5V (depending on load and LLC). Because it is dynamic it can help when using stepped overclocking, for instance 4 cores at x46, 3 cores at x47 2 cores at x48 and 1 core at x50 although you will need the higher c-states enabled for this.

Fixed voltage can improve latency. For instance offset and ATV work with VID which can mean voltage ramp up delays with the VRM and that means delay of increasing the frequency. With fixed voltage it can always be ready.
post #10 of 10
Quote:
Originally Posted by Carlos1 View Post

Clexzor: you have 3570k @ 4.9 Ghz using 1.408v on MB with no mosfet heatsink, wow smile.gif

unclewebb: that is very interesting idea. I believe many overclockers do not use c3/c6 states because of system instability. If the oced system is stable, than it indeed looks like better way than using EIST for underclocking and undervolting.

lol yeah using an H100i for cooling don't need any heatsinks added...never goes above 80c gaming IBT runs on max will however max the temps to 100c but doesn't matter I never use 100% load more than couple mins.
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