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Test Setup

Undervolting Your Phenom II And Core 2 Processors
By
System Hardware
Hardware
Details
CPU AMD
AMD Phenom II X4 955 (45 nm, 3.2 GHz, 4x 512 KB L2 and 6 MB L3 Cache, TDP 125 W, Rev. C2)
CPU Intel
Intel Core 2 Extreme QX9650 (45 nm, 3.0 GHz, 12 MB L2 Cache, TDP 130 W, Rev. D0)
Motherboard (socket 775)
MSI P45D3 Neo-F (Rev. 1.0)
Chipset: Intel P45, ICH10R
BIOS: 4.2 (02/18/2009)
Motherboard (Socket AM3)
MSI 790FX-GD70 (Rev. 1.0)
Chipset: AMD 790FX, SB750
BIOS: 1.3 (04/01/2009)
RAM DDR3 (Tripple)
2 x 2 GB DDR3-1600 (Corsair TR3X6G-1600C8D 8-8-8-24)
Graphics
Zotac Geforce GTX 260²
GPU: Geforce GTX 260 (576 MHz)
Graphics RAM: 896 MB DDR3 (1998 MHz)
Stream Processors: 216
Shader Clock: 1242 MHz
Hard Drive
Western Digital VelociRaptor, 300 GB (WD3000HLFS) 10,000 RPM, SATA/300, 16 MB Cache
Blu-Ray Drive
LG GGW-H20L, SATA/150
Power Supply
PC Power & Cooling, Silencer 750EPS12V 750W
AMD Software and Drivers
Operating System
Windows Vista Enterprise Version 6.0 x64 Service Pack 2 (Build 6000)
Drivers and Settings
AMD Chipset Drivers
Catalyst 9.4
Nvidia GeForce Driver
GeForce 185.85
Intel Chipset Drivers
Chipset Installation Utility Ver. 9.1.0.1012
Intel Storage Drivers
Matrix Storage Drivers Ver. 8.8.0.1009
Benchmarks and Settings
PCMark Vantage
Version: 1.00
PCMark Benchmark
Prime 95
Version: 25.7
In-place large FFTs


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Top Comments
  • 20 Hide
    johnbilicki , July 14, 2009 6:27 AM
    Glad to see this article considering I underclock a whole heck of a lot more then I overclock; working on the web doesn't require the same amount of power as playing a video game.

    My main concern is heat, I live in Florida right now and underclocking my computer and reduce the overall room temperature which is clearly higher then the average temperature of the rest of the house.

    What is nice about the Phenom II series is that I can drop my X3 720 BE from 2.8 to as low as 0.8 and adjust the cores individually. This let's me keep the first core at let's say 1.4 and drop the other two to 0.8 if I need my system running but won't be directly using it. I'm curious as how this effects the effective voltage if at all. My socket 939 Opteron 185 could only drop from 2.6 to about 1.8. Another thing to note is that CPU usage seems to have a much higher correlation to heat output; if my system is idle then it doesn't generate as much heat as if I was playing a video game.

    I was disappointed that the feature in the GeForce series that completely turned the video card off when not using 3D mode was removed. I prefer having one system to do my work and game and reducing heat output is my highest priority when I'm not spray-painting in Counter-Strike.
  • 11 Hide
    johnbilicki , July 14, 2009 6:41 AM
    @sohei Imagine being able to get 100mpg on a Ferrari...and when you want to kick it up a notch restore the normal power level. Less power means less heat...and it also means a smaller power bill. If entire data centers did/do this when demand is low they could/can save a ton of money.
Other Comments
  • 20 Hide
    johnbilicki , July 14, 2009 6:27 AM
    Glad to see this article considering I underclock a whole heck of a lot more then I overclock; working on the web doesn't require the same amount of power as playing a video game.

    My main concern is heat, I live in Florida right now and underclocking my computer and reduce the overall room temperature which is clearly higher then the average temperature of the rest of the house.

    What is nice about the Phenom II series is that I can drop my X3 720 BE from 2.8 to as low as 0.8 and adjust the cores individually. This let's me keep the first core at let's say 1.4 and drop the other two to 0.8 if I need my system running but won't be directly using it. I'm curious as how this effects the effective voltage if at all. My socket 939 Opteron 185 could only drop from 2.6 to about 1.8. Another thing to note is that CPU usage seems to have a much higher correlation to heat output; if my system is idle then it doesn't generate as much heat as if I was playing a video game.

    I was disappointed that the feature in the GeForce series that completely turned the video card off when not using 3D mode was removed. I prefer having one system to do my work and game and reducing heat output is my highest priority when I'm not spray-painting in Counter-Strike.
  • 11 Hide
    johnbilicki , July 14, 2009 6:41 AM
    @sohei Imagine being able to get 100mpg on a Ferrari...and when you want to kick it up a notch restore the normal power level. Less power means less heat...and it also means a smaller power bill. If entire data centers did/do this when demand is low they could/can save a ton of money.
  • 3 Hide
    stumpystumped , July 14, 2009 6:52 AM
    Even though the use of an top of the line Intel CPU is pointless, the article makes a valid point. Undervolting can save money and you can undervolt even more if you downclock as well. E5200 might be one of the best overclocking CPU but if you are using it in a HTPC like I do, 2.5G isn't really required to watch movies, listen to music or surf the web on the TV. I downclocked it to 2G and set voltage to 1.00V in BIOS. In Windows it sometimes goes as low as 0.82V. In referenece to johnbilicki's comment about GeForce CPUs, if you use nTune (I can't remember the new name for it) you can downclock you GPU to 25% of the factory setting and boost it to 100% or more when you are playing games.
  • 3 Hide
    jongwoonkim , July 14, 2009 7:06 AM
    excellent article. didn't have a clue about undervolting.
  • 1 Hide
    jongwoonkim , July 14, 2009 7:18 AM
    i don't like using i*t word so i won't use it. no company i know undervolt. and most computers are not oc'ed. and lastly but mostly undervolting doesn't reduce performance. get a job.
  • -1 Hide
    lapoki , July 14, 2009 7:37 AM
    But would you still love your ferrari if it sipped fuel even while sitting pretty in your driveway?
    And besides its not like you're crippling it for life, just resting while you sit on your a** doing nothing
  • 0 Hide
    jongwoonkim , July 14, 2009 7:46 AM
    on my Q6600,
    1.3v idle 186W, 100% 271W
    1.1v idle 170W, 100% 243W
  • 2 Hide
    rdawise , July 14, 2009 7:50 AM
    soheithe cpus use in the article are inappropriate if you want to show ,to bring in front economy, green computing etc ...you use components made for this undervoltage because if someone needs less heat and power consumption will newer buy components how from star use a lot of power because a high end cpu needs a high end motherboard high end gpu etc both amd and intel has this kind of products made for green computing


    Ture if you aim was simply "green computing". What if you simply want to save power for a short period of time, then wish to return to your "heavy load"? The problem with going simply "green" cpu is they lack horse power period. As you've pointed out they're not meant for heavy work. I guess an appropriate analogy would be having a car the could go 200 mph, but always doing the speed limit (let's assume 60). Would you rather have a car that could only do 60, or have a car that is capable of 200 if you need it to? That's my idea of it anyway. Good article.
  • 1 Hide
    andrej_valand , July 14, 2009 8:00 AM
    Nice article, i underclock my workstations notebooks and servers all the time for longer battery life and less power use. I use RMclock from RrightMark, it works excellent and it changes multiplier and voltage on the fly in windows depending on the load. So "sohei" no restarting is needed. Just Like "jongwoonkim" said you can have a efficient Ferrari which can go full when you need it to go fast... Regards
  • 0 Hide
    one-shot , July 14, 2009 8:16 AM
    I think there is a typo on page 4 it states "It turned out that the default voltage of 1.32 V could be lowered by as much as 12%, to 1.1175 V. This lowered system peak power from 216 W to only 179 W, which represents a 17.2% drop in system power consumption."

    However, in the graph, it shows 1.175Vcore. These are very different and I would like to know which one is correct. Thanks
  • 2 Hide
    andrej_valand , July 14, 2009 8:25 AM
    Yes that is true a high power cpu will consume more, but if you want and need to have an hi-end system with fast processor you buy it. True? But mostly you don't need full power all the time. Why not save something on the electric bill and do something for the planet and adjust the factory power management to even lower levels if it is possible? I see only positive points in that. Why would i buy a low power CPU if it is not enough for me? The article is just fine, because what I have found out that low power CPUS don’t underclock that well, they are already power optimized, but you can tweak the hi power CPUS for quite a high margin sometimes. But in my opinion it is better to use some dynamic underclock utility that as doing this. I agree with you doing this in BIOS makes less sense, and when the CPU goes to idle it destroys the settings, so that way the bad numbers for the AMD cpu at idle when its most important. If you want to do it right you have to control the multiplier and voltage all the time, depending on load.
  • 1 Hide
    drealar , July 14, 2009 9:49 AM
    LoL sohei, chill :) 

    @ PSchmid and ARoos
    "The power savings of 17.2% or 37 W..."
    "148 W instead of 185 W—that’s a 20% reduction." = 37W
    This is why I never rely solely on percentage%.. hehe

    As not so enthusiast & not so average user, I appreciate the fact that we're able to see what effect do SStep & C'n'Q have on undervolting.

    One thing that I'm wondering is how much is the CPU usage when running a process? Like if I see a 40% CPU usage normally, does that means I'll see 45~50% usage after undervolted? Or will I still see 40% but with a lil slower processing? Heh, I kinda got confused there, but would be useful to know since my CPU usage never goes beyond 70%.

    Another thing I wanna confirm is, I assume that undervolted cpu speed will be a tad slower; like 2.8GHz cpu's performance will be like a 2.6GHz cpu, except that now the 2.8GHz will use ~37W less than the 2.6GHz. Is it? Something like a strong muscular guy effortlessly lift a full tower PC compared to a thin muscle-less guy who give his all :p  :D 

    Would appreciate some clarification there Tom's guys :D 
    Please.
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