Liquid3D reviews Alphacool Cape KC42-X2 water block

[jaydee]

I actually think he is improving some. BUT I think he dosn't understand C/W to well. http://www.madshrimps.be/?action=get...56&articID=288

Originally Posted by Liquid3D

Using Hans Chung's freeware program CPU Wattage Calculator we can extrapolate the approximate wattage output of our Prescott 3.0E while overclocked 3750MHz and at 1.465Vcore to be 126.29W. Applying the required data for the C/W aspect of the Calculator we get a C/W rating (during Idle) of 0.079-C/W (indicated below).

I was under the impression that a CPU in idle state isn't using max wattage. If I am reading this right he used the max wattage (which is wrong to begine with as that estimator program should not be used in reviews as it is wrong) of said overclocked CPU in the equation (which means the CPU would be under full load not idle load?). What is even more troubling is the final answer. .079?

Also I noticed in his picture he uses a case temp and CPU temp to get a C/W? How can he be using a case temp when that is wrong. Main reason is the setup is not completely in the case and the side cover is off with rad outside of case?

Maybe I am just not reading things correctly....

Anyway I think his technique is a little better. Less big words and his computer appears to be off the ground and not by the window anymore.

[redleader]

I think he mixed up his numbers. From the screen shot it looks like he put the overclocked chip frequency in with the non-overclocked CPU temps. At least thats the only reason I can think that the numbers he shows don't match the ones on the chart or the screen shots . . .

Regardless, those wattage calculators are random if used correctly, and he didn't put the correct wattage in for the CPU, so he'd have the wrong (already incorrect) figure anyway.

Maybe 3 consecutive mistakes make a right?

[ymboc]

... fair enough, but (I presume) JD was implying that he should have known something was wrong because the value he got (0.079) is simply unrealistic.

[jaydee]

I see the article was edited since I posted this.

Originally Posted by Liquid3D

Using Hans Chung's freeware program CPU Wattage Calculator we can extrapolate the approximate wattage output of our Prescott 3.0E while overclocked 3750MHz and at 1.465Vcore to be 126.29W. Applying the required data for the C/W aspect of the Calculator we get a C/W rating (during Idle) of 0.12669 C/W (indicated below).

I still don't understand the idle thing. There is no way he can tell the wattage of a CPU at idle without very spacific equipment.

[BillA]

and yet again one has to question the competence of those 'running' the site,
still haven't figured out the proofing thing

[pHaestus]

Just because the W calculater says a CPU is generating a certain value doesn't make it so...

I still don't trust those calculators for a simple reason: If you change the multiplier of an AMD CPU to make it run at a higher speed without changing the FSB or voltage, then it IS effectively that higher speed CPU. But the calculators predict that it would actually generate more watts. Unless they've changed in the last few months anyway...

[pHaestus]

The calculation of a C/W for a running system is really tricky. The better your wb the higher percentage of the CPU's heat that goes into the water instead of the mobo's traces. The design of the mobo (layout of VRMs and other hot bits; cooling of the northbridge, etc etc) also will affect the heat load. It's not easy to do at all.

Now presumably if you use the same "W" every time then you're just adding a standard error into the results. The concern of course is that the whole purpose of a "C/W" is to produce results that are usable by other people. They aren't often qualified as "C/W*"

*for an IDENTICAL system in every respect including bios rev, psu, ram, mobo, cpu, video card, etc etc

I find the use of C/Ws for testing on real systems to be somewhat disingenuous because you're putting another layer of math between the user and the actual results. It isn't the case in this review because the raw numbers are still reported, but it often happens.

[redleader]

Originally Posted by ProBerto

according to the link of the Watt Calc:

P4-3.0E = 89W
http://users.erols.com/chare/elec.htm

I think Vcore * Imax would be a better measure, but if the calc says to use those numbers, then you should probably use those numbers.

Either way, its just a ballpack figure calculated from a few EE rules of thumb, so I would not trust it.

[jaydee]

Ok, glad I am not the only one seeing the problem. Props to Liquid3D for at least trying to making progress on the quality of his reviews.

[Butcher]

89W is the TDP (thermal design power) for a prescott, NOT the actual heat output. It's a number Intel calculated to give heatsink manufacturers a maximum number to aim for. Using it as a basis for actual output is highly suspicious. Vcore*Imax is probably a better number, but still dubious - not all that power goes out the top of the core. Besides which it's virtually impossible to drive a CPU hard enough to hit Imax outside of lab testing.

[pHaestus]

Intel does make a program specifically designed to generate max watts. AMD has one too but they dont make it available to plebians like myself.

[Roscal]

No it's not public, it's called P4PowerMax

[pHaestus]

The old one for the P3 core was freely available I believe.

[andy497]

Originally Posted by Roscal

No it's not public, it's called P4PowerMax

I saw a French site that mentioned this in an article on cpu power consumption. Looks like a pretty good article, but my French is non-existent, so I had to try to make sense of a google translation.

translation:
http://translate.google.com/translat...php%3Fid%3D114

original:
http://www.x86-secret.com/popups/art...dow.php?id=114

No link to download p4powermax however. Maybe it's circulating on p2p...