Undervolting Your Phenom II And Core 2 Processors
Table of contents
- 1. Efficiency For Free: Core 2 Quad And Phenom II X4 At Reduced Voltage
- 2. Platforms: AMD 790FX And Intel P45
- 3. The Basics Of Undervolting
- 4. Undervolting AMD's Phenom II X4 955
Enthusiasts generally try staying up to date when it comes to overclocking processors. They spend a lot of time answering these sorts of questions: How fast can certain processors go? What voltage levels do you need to get there? And what’s the best cooling solution?
But while overclocking lets you bump CPU performance to the levels of more expensive processor models, it is also possible to go in the other direction. You can typically undervolt a processor in an effort to improve efficiency without affecting performance at all.
Voltage, Clock Speed, and Power Consumption
Clock speed is one of the biggest determinants of performance, and increasing voltage is typically an action taken to enable higher clock speeds. With that said, voltage plays the most important role in establishing power consumption, with clock speed playing a secondary role in that arena. Increasing or decreasing clock speeds has a straight proportional impact on power, while power actually scales with the square of voltage. For this reason, bumping up voltage always has a more significant impact on power consumption than a clock speed increase.
And of course, reducing the operating voltage can have a significant impact on power consumption, which is why we decided to look into it.
Lower Voltage Products
Many mobile processors are simply modified, low-voltage versions of common products. Think of Intel’s Core 2 mobile processors. These are power-optimized, but under comparable conditions, they would perform and consume power like their desktop brothers. The Core 2 Duo T-series is rated at a maximum power consumption of 35 W, the P-series stays within a 25 W envelope, and so forth.
But there are low-power parts for desktop systems as well. AMD offers energy efficient processors with the suffix “e” (Phenom II X4 900e, 905e, and the Phenom X4 9350e). Intel is offering Core 2 Quad “S” models, which deliver the same performance as the regular models, but within a 65 W thermal envelope instead of 95 W. Although the lower-power processors are too expensive, if you ask us, they don’t fail to impress, as both the idle and peak power of test systems decreases.
Low-Voltage CPU Do-It-Yourself?
So what if we were to tweak CPU voltage ourselves? If overclocking and overvolting have become so popular, it couldn’t hurt to try some undervolting. We setup two MSI motherboards that we had at our disposal: a P45D3 Neo, which we recently used to find the perfect Core 2 Duo overclock, but this time with a Core 2 Extreme QX9650, and a 790FX-GD70, allowing us to test AMD’s Phenom II X4 955.
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.
this is old stuff
every company with a decent it department do this undervoltage and more
but is a nice article for those who doesn't know
but but but who needs a high end cpu needs his power and use this extra voltage for OC
so undervoltage with high-end is illogical in many ways
who buys a ferrari and cripple it?
@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.
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.
i understand that..less power less heat, i do myself undervoltage and underclocking for pc's used for surveillance how needs just to stay on and cool .
but nobody will buy a high end CPU ( PC ) for undercloking or undervoltage
High end means high demand of course we do not talk about people who buys PC just after brands not from necessity
the 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
excellent article. didn't have a clue about undervolting.
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.
johnbilicki every cu has undervoltaage and underclocking by default
in this article above they done an manual undervoltage that takes time , restart for different cpus restart ...so this is not just a push of a button.If you need a manual undervoltage that cpu will stay undervoltage for some time, days, months, years
if you buy a ferrari i am confident you will never cripple it you will buy something for make it faster
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.
yes * * because all cpu have + voltage by default i bet you don't have a clue ...get a girl friend
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
on my Q6600,
1.3v idle 186W, 100% 271W
1.1v idle 170W, 100% 243W
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
you have a point here but all i am trying to say that manual undervoltage is not something to push a button so in many cases if you need green computing you buy something that use less energy from the start ..and tom used 2 cpus inappropriate for this review
but if he want to shows again that intel is the choice ok.. he made his dark point again
the 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.
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
i did not say is a bad idea to undervoltage ,i use this undervoltage for a lot of pc's... but manual undervoltage is not practical if you don't really need it and if someone buy a high end cpus i think he will not do undervoltage to often you will need more often power from a high end cpu than less energy or heat
but if intel or amd make this extreme low voltage operation an automatic feature is a great thing until than a review with high end cpus is pointless
laptops have this feature but a laptop is a laptop
and this is the answer why they don't included this feature because a desktop doesn;t need it ...and if you really need it you can buy a low power cpu and undervotage or overclocking
again is odd to write an article about low power with high power cpus
A high power cpu will still consume a lot even with undervoltage
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
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.
"Can the Intel system beat the 17.2% reduction in peak power?"
what the f... is that you want to show us ? what?
that undervoltage make this earth better or this intel cpu is low power that p2 955?
Marketing again
get my point ? is not about ecology is about money...intel's money