Desktop CPU Power Survey, April 2006
Posted: Wed Apr 05, 2006 1:55 pm
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Isn't CnQ just going to set it back to the default vcore at 2.2ghz?dragmor wrote:Great article, makes me feel even luckier that my 3500+ has a TDP of 36.4w (although the TCaseMax is only 55c).
Since I've got it undervolted to 1.2v I'm guessing its about 25w at full load + CnQ sets it to 1ghz with 0.925v at idle
Not according to speedfan and XPC tools. I think the CnQ implementation on the shuttles is slightly different. It seems to just change the multipler between 11 (default) and 5, and drop / raise the vcore by ~0.3v. I would use Crystal but the bloody thing wont let me set the vcore below 1.1v. Its a shame because the CPU can do [email protected] and [email protected], but the machine requires a 1.2 vcore to cold boot.winguy wrote:Isn't CnQ just going to set it back to the default vcore at 2.2ghz?dragmor wrote:Great article, makes me feel even luckier that my 3500+ has a TDP of 36.4w (although the TCaseMax is only 55c).
Since I've got it undervolted to 1.2v I'm guessing its about 25w at full load + CnQ sets it to 1ghz with 0.925v at idle
It depends what you define as 'small'. For example the Vcore difference between the highest and lowest P-states of my Sempron 3300 is only 0.3V, but at 1Ghz @ 1.1V it can be run passive, whereas at 2Ghz @ 1.4V it cannot. The relationship between CMOS supply voltage and power output is quadratic, so IMHO small reductions can make a big difference to overall heat output.Small reductions in Vcore cannot improve power demand dramatically
Don't the AMD CPUs have much more L1 cache?L1: 16k, L2: 512 kB (Manchester)
L1: 16k , L2: 1MB (Toledo)
But you changed more than just vcore.jaganath wrote:It depends what you define as 'small'. For example the Vcore difference between the highest and lowest P-states of my Sempron 3300 is only 0.3V, but at 1Ghz @ 1.1V it can be run passive, whereas at 2Ghz @ 1.4V it cannot.
Yeah, L1 cache should be 128k for all the A64 chips.Olaf van der Spek wrote:Don't the AMD CPUs have much more L1 cache?
I noticed a 6c drop in full load temps between 1.4v and 1.2v.Olaf van der Spek wrote:But you changed more than just vcore.jaganath wrote:It depends what you define as 'small'. For example the Vcore difference between the highest and lowest P-states of my Sempron 3300 is only 0.3V, but at 1Ghz @ 1.1V it can be run passive, whereas at 2Ghz @ 1.4V it cannot.
I think there are several boards which operate like this. The Shuttle is probably just changing the actual voltage not manipulating the processor VID. Some boards can do both. I think my TForce 6100 operates like your Shuttle--at least for overclocking/overvolting it does. The effect of the C'n'Q changes is to manipulate the VID, the motherboard simply offsets the requested VID by the difference you've selected in the BIOS.dragmor wrote:Not according to speedfan and XPC tools. I think the CnQ implementation on the shuttles is slightly different. It seems to just change the multipler between 11 (default) and 5, and drop / raise the vcore by ~0.3v.
OK, I'll give you a different example. The P4-M chip in the computer that I am writing this on is currently running 1.86Ghz @ 1.038V; at exactly the same clock speed but increasing the Vcore to 1.3V, it can no longer be run passive (at least not without triggering thermal clock throttle mechanism); so we can see that the supply voltage to the CPU really is the primary determinant of heat output.But you changed more than just vcore.
I think the point wasn't to test every possible CPU. But to give a general idea based on what CPUs they had available which are many of the more common ones.QuietOC wrote:While I appreciate the article. I can't help but wonder at some of the CPU choices. It seems like a lot of them were not the best representatives of their kind.
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Wow, 0.88V? I thought that most E6 cores had trouble getting below 1.2V I was excited that my E6 Sempron 64 2600+ got down to 1.05V. Although I didn't see much difference in thermals between 1.2V and 1.05V.QuietOC wrote:y new E6 Sempron 64 2500+ was able to run the same speed at 1.08V (not to mention running at its default speed at 0.88V)
No, I just expect the lowest-power CPU's of each line tested. SPCR could sell off these old chips and buy these low-end/latest process processors. So, I can't see cost being the reason not to get the best examples.BillyBuerger wrote:I think the point wasn't to test every possible CPU. But to give a general idea based on what CPUs they had available which are many of the more common ones.
Hardly, I even had a 130nm A64 2800+ running on 0.850V. The point is what clockspeed can these run that low on. For my $70 E6 S64 2500+ that is its default (rather low) clockspeed of 1.4GHz.Wow, 0.88V? I thought that most E6 cores had trouble getting below 1.2V.
Very kind words, thank you.oldabelincoln wrote:As fine a piece of work as I've seen in 45 years in computers.
Bravo.
You must think we have big $$$ to spend on gear. Processors cost $, our finances are limited, and we take what we can get from whoever is willing to give/lend us the gear. The CPUs are a sampling of commonly used models. They were deliberately NOT chosen for min power, but for reasonably wide availability for average buyers.QuietOC wrote:While I appreciate the article. I can't help but wonder at some of the CPU choices. It seems like a lot of them were not the best representatives of their kind.
rev DH8-E6 Venice. Re- your Sempron, I quote from the article:QuietOC wrote:Was your Sempron a D0 chip?
The power consumption characteristics of processors varies from sample to sample within the same model and stepping. It can vary as much as >10%, according to some sources, although it is probably considerably less than that on average. It is exactly the same variance that makes some individual processor samples easily overclocked (or undervolted) and others not overclockable at all. We have a mix of samples, mostly provided directly by Intel and AMD, mostly only one sample of each model. Our results are probably more or less repeatable but it would be a surprise if anyone obtained identical results with a similar collection of samples. Our results are good general indicators, but please don't assume that because our sample managed to run stable at 1.15V on our particular motherboard that all samples of the same CPU model can do the same. Also, don't base your buying decision between two closely ranked processors on the basis of any single result we report. Price, suitability, availability, peripherals, ease of implementation — these are all important buying considerations.
Have you tried to buy one? Intel did not have a sample for me & it was not possible to find one in Vancouver in time for the testing. AFAIK it does not have wide distribution at this time.QuietOC wrote:Pentium 4 630??? Why not the 65nm Pentium 4 631?
Have you tried to buy one? See first comment aboveCore Duo T2600??? Why not the L2400?
Nice doesn't mean it's doable.Also it would have been nice if both the S754 and S939 motherboards at least used the same chipset.
That's fodder for another article altogether, and this article was massive enough to complete. Besides, there are too many other factors (components on the boards) to isolate just the chipset alone. VRM efficiency & chipset both affect power readings, for example, as would different audio, graphics, LAN & other chips. This task would require test plaform choices of a different nature.The power efficiency diferences between the different integrated chipsets would also be nice to know, but this review could have at least shown the difference single and dual channel DDR make using the same chipset.
Wrong interpretation, imo.Looking at the Sempron results seem to show that most of the Turion's advantage over the Athlon 64's is its platform, not the CPU iteself.
Didn't you read the article? Each CPU was carefully undervolted to instability, then raised back up. Your experience differs from ours, but that's hardly proof of anything.Also was no attempt made to undervolt the processors at the lowest state? It seems like the low state voltages of the A64's were way too high--seeing as my Sempron 2500+ can operate at 1.4GHz @ 0.88V. An E6 A64 should be able to go down to at least 0.85V @ 1.0GHz, if not lower.
Mike, I did appreciate the article. I also greatly appreciate your site.MikeC wrote:You must think we have big $$$ to spend on gear. Processors cost $, our finances are limited, and we take what we can get from whoever is willing to give/lend us the gear.
Yes, I see you found the lowest voltage for the high-state, but it looks like the low-state (the 1GHz speed) setting was using the default C'n'Q voltages. These are the voltages that affect the idle power consumption, and the greatest power savings would be relealized by finding the lowest voltages for that state.Didn't you read the article? Each CPU was carefully undervolted to instability, then raised back up. Your experience differs from ours, but that's hardly proof of anything.Also was no attempt made to undervolt the processors at the lowest state? It seems like the low state voltages of the A64's were way too high--seeing as my Sempron 2500+ can operate at 1.4GHz @ 0.88V. An E6 A64 should be able to go down to at least 0.85V @ 1.0GHz, if not lower.
Mmm, it's really unfortunate that Newegg does not ship to Canada.QuietOC wrote:I am guessing that you can't sell all those old expensive chips then? The Pentium 631 has been available at Newegg for quite some time. And, yes, I do know that it is impossible to find new Intel chips through normal distributors.
Ah, I'm sorry, I misread your original comment. Yes, you are right, we did not check this. It could and probably should have been done, but with so much testing, it got missed. You could easily generalize, however, that a proportionate drop in idle power of at least 10% at the 2x12V socket could be seen across the board if the CPUs were undervolted at idle. If you charted this graphically, I doubt its shape would be much different than the stock idle power.QuietOC wrote:Yes, I see you found the lowest voltage for the high-state, but it looks like the low-state (the 1GHz speed) setting was using the default C'n'Q voltages. These are the voltages that affect the idle power consumption, and the greatest power savings would be relealized by finding the lowest voltages for that state.
I remember P4 Northwood's with C1 stepping had very variable capability when it came to overclocking; factors such as location of manufacture, date of manufacture and batch number all seemed to be (contra-) indicators of overclockability. Some of the truly great C1 Northwoods (such as the SL6RZ and the SL6GQ) could hit 4Ghz and beyond, whilst the rubbish ones from the Philippines and Malaysia rarely broke 3Ghz.FWIW: I have not observed large variations in the overclocking capability of CPUs of the same core/stepping.
My E3 Athlon 3000+ can do about 1.125V at stock speeds just fine and probably far less with underclocking. I think there's plenty of overhead as long as you're not pushing the mhz too high. I currently run at 2.24ghz at 1.225v and I that gives me about a .05v cushion for stability over my lowest tested voltage. I've noticed some pretty big thermal differences myself, I can never get over 40-42C at full load with my current voltage/ambient temps and stock would definitely go around 50C.Wow, 0.88V? I thought that most E6 cores had trouble getting below 1.2V I was excited that my E6 Sempron 64 2600+ got down to 1.05V. Although I didn't see much difference in thermals between 1.2V and 1.05V.
Mike, if you would like to borrow my E6 Sempron 64 2500+, I'd be happy to send it to you. Let me know.Hifriday wrote:After all that work I'm sure you're just glad to have finished. But if you are willing to consider adding more CPUs to the list, I believe fellow SPCRers including myself would be willing to pay for the purchase of certain CPUs for testing and have SPCR send them to us after you've finished.
Me too!merlin wrote:Mike, this is an awesome article and I love how much data is presented regarding the power consumption and large effects of undervolting and/or underclocking on power usage. I'm sure you spent far too much time on this and you have our thanks for doing so!
That's a corporate-political issue, not an SPCR issue IMHO. It does not belong in Mike's article.merlin wrote:...intel loves using performance per watt as a buzzword and it would be great to see how their current processors compared to what they're saying for merom/conroe.
Yes; sometimes it's imperative to remember that SPCR basically operates on a shoestring budget, with only one full-time employee (AFAIAA). That said, the impulse to "improve" articles is a good instinct, as that way an article can "evolve" with later accretions making it into a kind of "super-article"; this CPU article is a good candidate for that process IMHO.If I hadn't made the mistake of posting a coupla trivially simple fan "review"s, I would not believe some of the above criticism! I independently discovered that SPCR persons are highly demanding; they want what they want and they want it now!