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Does undervolting still kill these chips? - Page 3

post #21 of 27
Detailed explanation of how a microprocessor works so you can better understand exactly what's going on!

A microprocessor is basically a ton of capacitors getting charged and discharged every clock cycle (MOS transistor acts like a capacitor). Lower the clock speed and the amount of charging/discharging goes down. Lowering your clock speed WILL reduce heat generated.

As a capacitor is charged up, the time constant, Tau (greek letter, where Tau=Capacitance*Resistance of resistor in series with capacitor), greatly effects how quickly the capacitor can charge/discharge. The voltage across the capacitor is modeled by V=Vcore*e^(-T/tau) where e=2.71 and T is time. Vcore is your CPU voltage.

If you lower your clock speed, the capacitor has more time (Time=1/frequency) to charge up and thus your Vcore can be set lower in order charge the capacitor to the proper voltage. This is many people find the need to raise they're Vcore when they up the clockspeed.

Power=Voltage*Current
As you lower the voltage, then your power goes down. (Also note that since Voltage=Current*Resistance that as you lower Voltage, Current also goes down a bit) You gain 2X here since your CPU will draw less power from the wall, and also generate less heat which means that your AC will do less work trying to keep your room cool. How much you gain depends on how much you are willing to underclock your CPU.

Also note that as the CPU heats up, it's resistance will increase, thus requiring move voltage and drawing more current, causing it to heat up even more. The cooler you run your CPU, the more efficiently it runs.

Also, Intel speedstep will automatically underclock the CPU when it is idle. My Q6600 steps down from 1.24v to 1.13v and 2.4ghz to 1.6ghz when idle. Make sure speedstep is enabled.

Another tip, take the GPU out of that rig if it's just a server rig, as GPU seems to draw most of the power nowadays. If you can figure out how to encode your movies on the GPU (think nvidia CUDA, DXVA, i'm sure theres an app out there that will do that) instead of the CPU, then potentially great power savings that way too, since GPU is better at encoding than a CPU will ever be.

If you can decrease power draw by about 25 watts or so, you're looking at a savings of about $2 a month on your power bill from (if you run the PC 24/7) the power the computer draws from the wall alone. Up to maybe $5 if you account (I assume that for every watt of heat generated by the PC the AC uses a little more than a watt of power to cool) for the AC having to cool the room.
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post #22 of 27
Quote:
Originally Posted by Atomfix View Post
Detailed explanation of how a microprocessor works so you can better understand exactly what's going on!

A microprocessor is basically a ton of capacitors getting charged and discharged every clock cycle (MOS transistor acts like a capacitor). Lower the clock speed and the amount of charging/discharging goes down. Lowering your clock speed WILL reduce heat generated.

As a capacitor is charged up, the time constant, Tau (greek letter, where Tau=Capacitance*Resistance of resistor in series with capacitor), greatly effects how quickly the capacitor can charge/discharge. The voltage across the capacitor is modeled by V=Vcore*e^(-T/tau) where e=2.71 and T is time. Vcore is your CPU voltage.

If you lower your clock speed, the capacitor has more time (Time=1/frequency) to charge up and thus your Vcore can be set lower in order charge the capacitor to the proper voltage. This is many people find the need to raise they're Vcore when they up the clockspeed.

Power=Voltage*Current
As you lower the voltage, then your power goes down. (Also note that since Voltage=Current*Resistance that as you lower Voltage, Current also goes down a bit) You gain 2X here since your CPU will draw less power from the wall, and also generate less heat which means that your AC will do less work trying to keep your room cool. How much you gain depends on how much you are willing to underclock your CPU.

Also note that as the CPU heats up, it's resistance will increase, thus requiring move voltage and drawing more current, causing it to heat up even more. The cooler you run your CPU, the more efficiently it runs.

Also, Intel speedstep will automatically underclock the CPU when it is idle. My Q6600 steps down from 1.24v to 1.13v and 2.4ghz to 1.6ghz when idle. Make sure speedstep is enabled.

Another tip, take the GPU out of that rig if it's just a server rig, as GPU seems to draw most of the power nowadays. If you can figure out how to encode your movies on the GPU (think nvidia CUDA, DXVA, i'm sure theres an app out there that will do that) instead of the CPU, then potentially great power savings that way too, since GPU is better at encoding than a CPU will ever be.

If you can decrease power draw by about 25 watts or so, you're looking at a savings of about $2 a month on your power bill from (if you run the PC 24/7) the power the computer draws from the wall alone. Up to maybe $5 if you account (I assume that for every watt of heat generated by the PC the AC uses a little more than a watt of power to cool) for the AC having to cool the room.
Seems pretty logical i was playing GTA IV before almost Maxed out, and it lagged like it never had. Probably because your explanation of not enough power getting to the CPU andno as much info being sent through. I was depressed so i have now overclocked to 3.7Ghz
post #23 of 27
so i dont mean to hijack but currently im running my i7 undervolted(-160mv precisely)...so does undervolting has demerits other than being unstable and bsoding....????
post #24 of 27
Doesn't have to be unstable or BSOD.

0.975 on an AMD CPU-NB seems way low. That's not just the memory controller, that includes the L3 cache as well. Really the power difference is negligible - I can't measure the difference with my killawatt under 1.20v. Much like changes in low vcore - take my overclocked CnQ setting, 940 MHz at 1.07v, that eats 128 watts at idle. I drop to 800 and 0.88v, and it goes to 126 watts. Whoopie.

Then again, my CPU-NB is not stable with anything less than 1.18v or so at any speed. Been that way since the day it arrived. My chip is a BUM steadman!
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post #25 of 27
Thread Starter 
Left my CPUNB at the stock 1.175v now, cba to fiddle with it.

Also, am not doing it for the power savings, but for the sake of not blowing the 4+1s on my board. It's 2hr OCCT/2hr Prime/50 pass IBT stable so I'd be surprised if the undervolting takes a performance hit, but you never know.

Gonna do some IBT and FC2 benchmark loops on 3.12GHz/1.275v and 3.12GHz/1.425v (stock volts) when I get the chance, and will post FPS results back.
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post #26 of 27
Not sure if anyone has mentioned, but it looks like your topic title is a little ambiguous.
Undervolting, in general, refers to VCore, and it seems like a few people have been responding to just that, rather than undervolting CPU/NB ("delta between the CPU memory controllers and the RAM").

Undervolting VCore is fine. I ran 3.2 @ 1.15V and 0.8 @ 0.8V for 6-7 months (during summer/fall), with K10Stat.

Undervolting CPU/NB, on the other hand, I have no idea.
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post #27 of 27
Thread Starter 
Quote:
Originally Posted by lvlrdka22 View Post
Not sure if anyone has mentioned, but it looks like your topic title is a little ambiguous.
Undervolting, in general, refers to VCore, and it seems like a few people have been responding to just that, rather than undervolting CPU/NB ("delta between the CPU memory controllers and the RAM").

Undervolting VCore is fine. I ran 3.2 @ 1.15V and 0.8 @ 0.8V for 6-7 months (during summer/fall), with K10Stat.

Undervolting CPU/NB, on the other hand, I have no idea.
'Tis not just regarding the CPU/NB, it's both.
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