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Undervolting i7 920 - Worth it?

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November 17, 2009 6:31:40 PM

Just got rid of my stock cooler and installed a watercooling loop for both my CPU and GPU. Idle temps went down from 48°C to 32°C so I'm happy now. I'm using an XSPC 360RX rad which is sufficient at the moment. I forgot to use Prime95 to test my load temps with the stock cooler but considdering the fact my CPU was capable of reaching 70°C while playing Crysis I guess Prime95 would have been able to push it in the higher 70's maybe even 80's.

Stressing my CPU 100% using Prime95 results in Load temps of 51°C maximum after an hour of stressing. I think this is pretty good. Even though my load temps are satisfying my idle temps seem a little high compared to my load temps.

So I think I have a choice here. I could either overclock my processor (C0 stepping) to 3.4GHz or higher because I think I have enough headroom altough this is just a gues, or I could undervolt my processor so I can reach lower idle temps. Because I have no experience whatsoever in overclocking I'm feeling more for the undervolt.

Problem is, I have no experience undervolting either and undervolting a core i7 doesn't seem to be a popular choice out on the net. I only found 2 guides for undervolting and still they were not what I was looking for. Also, my CPU currently auto adjusts the Vcore and frequency to lower the temps a bit so I wonder if undervolting my processor to let's say 1.04V will have any effect on the temps because it already lowers the Vcore to 1.024V when the load is below 10%.

SO I ask you, is undervolting a smart choice here? And what are my other options besides overclocking this b* because I don't feel like OCing since the 920 is far from a bottleneck in my system.


Your input please. :bounce: 

More about : undervolting 920 worth

a c 159 à CPUs
November 17, 2009 8:57:21 PM

No. The speedstep option already lowers it automatically. You don't save anything. Remember that your video card and motherboard typically use the most juice. When overclocking, you'll see a spike above 200 watts. The real choice is to check the stability with speedstep enabled while overclocking.
a b à CPUs
November 17, 2009 9:15:39 PM

I undervolted my i7 920 to 1v, defaulting to .95v, and my idle temps were in the low 30s'C, load temps running Prime95 didn't exceed ~54'C

However, it caused my CPU to use a higher multiplier the majority of the time, and idle power consumption increased to 46watts.

I currently have experimented with 1.05v (defaults to 1v) and 1.625v (defaults to 1.02v) and they use 42w and 41w at idle respectively. I'm going to stick with those two figures instead of extreme-undervolting since another person says under-volting can cause an increase in amperage draw by the CPU.

http://www.tomshardware.com/forum/270223-28-undervoltin...
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November 18, 2009 5:31:05 AM

Yeah I've read the same thing. But I don't realy care about the power consumption because I'm not overclocking and a few watts wont make that much of a difference in my opinion. It's the temps I would like to lower. Idle you get temps in the low 30's but what cooler do you use? And did you overclock the CPU?
November 18, 2009 8:23:36 PM

What is your ambient
a c 315 à CPUs
November 18, 2009 8:37:49 PM

What is your objective?

Just leave things at stock if you are not going to overclock for performance.

The cpu is designed to last a long time at stock with the stock cooler, so longevity is not an issue.
a b à CPUs
November 18, 2009 8:39:12 PM

Non-overclocked, Mugen2 cooler.

Room temperature ranges from 70'F to 75'F

At 1.15volts (defaults to 1.1v), the CPU ran at 38'C-43'C idle, 52'C-55'C gaming load.

At 1.0625volts (defaults to 1.03), the CPU ran at 35'C-39'C idle, 47'C-49'C gaming load.


So it runs about 3-4'C cooler when undervolted at idle, and 5-6'C cooler when undervolted at load.


November 18, 2009 10:25:54 PM

The idle doesnt really matter if its low enough

What does matter is your load which is fine

The reason the idle is high is probably because your gpu is also on the loop so it is generating heat also
a b à CPUs
November 18, 2009 10:42:25 PM

Black Hush said:
Just got rid of my stock cooler and installed a watercooling loop for both my CPU and GPU. Idle temps went down from 48°C to 32°C so I'm happy now. I'm using an XSPC 360RX rad which is sufficient at the moment. I forgot to use Prime95 to test my load temps with the stock cooler but considdering the fact my CPU was capable of reaching 70°C while playing Crysis I guess Prime95 would have been able to push it in the higher 70's maybe even 80's.

Stressing my CPU 100% using Prime95 results in Load temps of 51°C maximum after an hour of stressing. I think this is pretty good. Even though my load temps are satisfying my idle temps seem a little high compared to my load temps.

So I think I have a choice here. I could either overclock my processor (C0 stepping) to 3.4GHz or higher because I think I have enough headroom altough this is just a gues, or I could undervolt my processor so I can reach lower idle temps. Because I have no experience whatsoever in overclocking I'm feeling more for the undervolt.

Problem is, I have no experience undervolting either and undervolting a core i7 doesn't seem to be a popular choice out on the net. I only found 2 guides for undervolting and still they were not what I was looking for. Also, my CPU currently auto adjusts the Vcore and frequency to lower the temps a bit so I wonder if undervolting my processor to let's say 1.04V will have any effect on the temps because it already lowers the Vcore to 1.024V when the load is below 10%.

SO I ask you, is undervolting a smart choice here? And what are my other options besides overclocking this b* because I don't feel like OCing since the 920 is far from a bottleneck in my system.


Your input please. :bounce: 


Your processor is on water cooling and is at 32C?...I am not very knowledgable with cooling and stuff (not my speciality), but I am using an air cooler and i get 29-30Idle. And take into account that I am using a crappy old case where barely anything is actually mounted, just connected and has no strong air currents going through it...wait until I get my HAF932, then my temps will probably be even lower. I might be missing something about how this works but just pointing that out.
a b à CPUs
November 19, 2009 1:38:14 AM

wsupduck said:
The idle doesnt really matter if its low enough

What does matter is your load which is fine

The reason the idle is high is probably because your gpu is also on the loop so it is generating heat also


Idle temps are for peace of mind =)


GPUs temps are important too, but if it has any type of 2 slot cooler then it should be fine. My GPU actually dumps half the heat back into the case, but I'm still able to keep nice and cool.
November 19, 2009 2:12:53 PM

Indeed, my idle temps are fine, I never said they weren't. What I did say is that I think they could be better.

I have a Heatkiller 3.0 LT, 360RX XSPC rad so 32°C without even an overclock seems high to me. However I also have a GPU in my loop so maybe I shouldn't compare my temps with someone who is only cooling his CPU. The HD4850 is idleing at 35°C so that's a considderable amount of heat extra.

Hence the low increased temperatures when only my CPU is stressed. Maybe I should try and run Furmark and Prime95 at the same time. However, I'm using a swiftech mcw-60R Revision 2, in other words a non-full-cover block. And I totally forgot haetsinks for my memory on the graphics card so I burn my finger when touching them :) 

Furmark makes my card make weird noises lately, high pitch zoom. :cry: 
a b à CPUs
November 19, 2009 8:04:56 PM

^Uhm, well by mostly nothing being mounted i meant my SSD, PSU, and fans. The cpu,mobo,and GPU for me are mounted. My GPU (8800GTS) 640mb is a couple inches from my CPU right now and i still get those amazing temps. However my GPU is cooled by a double slotted PCI cooling fan that sucks everything out the bottom grills and a custom attacked little fan on the back that sucks everything out the rear grills. so my videocards heat is completely driven away. Yes if you think its weird how i get this on air....the cooler master V8 is just that freaken amazingly good. haha
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