66 Degrees -- Is that OK?
 

Hello,

Well, our new home theater PC is busily factoring away (and the Ceton quad-tuner TV card is finally shipping!), but I have a question about the internal temperature.

Before I installed the graphics card, the CPU temp would get to about 50C with Prime95 running. (The program runs for about 10 hours a day... and no, we're not actually [U]watching[/U] TV all that time, but we do tend to leave it on as background.) Ever since I put in the graphics card, that reading reaches 66C -- it must have done a number on the internal airflow. I'm a little worried because the CPU specs say that it can sustain a maximum 71C and summer is approaching. I don't want to end up shortening the CPU's lifespan. (It's an Athlon II X4 640.)

So my question is: Is 66C too close for comfort, or not really? And if it is, then what's the best way to lower that temperature while still keeping Prime95 running? I'm thinking of either upgrading the CPU fan, or installing an additional internal fan. Which is the better approach?

In case it helps, here is the manufacturer's spec sheet for the PC: [URL]http://h10025.www1.hp.com/ewfrf/wc/document?docname=c02628226&tmp_task=prodinfoCategory&lc=en&dlc=en&cc=us&os=4063&product=5049513&sw_lang[/URL]=

Thanks a bunch.

Rodrigo

Yeah, 66C should be quite fine. The 71C figure given by AMD is not actually the "real" maximum; that's what's called the [I]thermal spec temperature[/I], which is the point at which the CPU begins thermal throttling (slowing down the CPU to help it cool better). The actual maximum is generally in the vicinity of 85-100C (never as low as 71C, hence the conclusion that that is merely the thermal spec temperature) on most modern CPUs. Even that maximum, which if reached will cause the computer to immediately power down, should still be safe--the components won't actually start to be damaged until temperatures even higher than the maximum, which it shouldn't ever reach due to the shutdown failsafe.

Think of thermal throttling as a brake pedal for the CPU. When you reach the 71C thermal spec, it slows down just a tad, helping to maintain the temperature at that level and keep it from going any higher. If, however, it nonetheless does go higher (say, you have gradual dust buildup in the CPU cooler--that's usually the cause of high temperatures), the thermal throttling will be applied a little more. And so on, until you get to the TJunction Max temperature (the "real" maximum, the one that's likely somewhere around 85-100C), at which point the system will just power down.

As long as the temperature is below the thermal spec, you're quite fine--there's no risk to the CPU and it's running at full speed. The higher over the thermal spec you go, the more speed penalty there is (not very noticeable at first, but if you're, say, 10-15C over the spec, there will probably be a small but noticeable hit to your Prime95 output)--but there's still no risk of actual damage to the CPU. I usually try to clean the dust out of my CPUs whenever they get more to more than a few degrees over the spec (to keep them running at full speed) but if I don't get around to it for a while, I'm not going to sweat it if my CPU is hovering within <5 degrees of the TJunction Max (as long as it's not actually reaching it :smile:).

So, long story short, with a thermal spec of 71C, 66C should be quite fine for a routine baseline operating temperature. Dust can, of course, push it up higher, but you should be able to get it back to the old 66C by taking a vacuum to the CPU cooler once in a while. :smile: (Standard household canister vacuums work best--an upright should also work if it has a spot-cleaning hose.) If you ever want to try overclocking, you might need to upgrade the cooler to give yourself a little more "wiggle room" (since overclocking increases the baseline temperature), but at stock speed what you have should be quite fine.

mdettweiler,

Thank you for the detailed reply! That's just the sort of information I was hoping to get.

On this point at least, it looks like there's no real need for more tinkering with that PC. :tu::tu:

Now, on with "taping" that complete collection of "The Outer Limits." :smile:

Rodrigo

[QUOTE=Rodrigo;256262]

So my question is: Is 66C too close for comfort, or not really? And if it is, then what's the best way to lower that temperature while still keeping Prime95 running? I'm thinking of either upgrading the CPU fan, or installing an additional internal fan. Which is the better approach?

[/QUOTE]

Is Prime95 stable at 66 ºC?
The best way to lower you CPU temps is to buy a new cooler, like one from Noctua or ARCTIC COOLING - Freezer Xtreme Rev2. You need to verify the space for it because some coolers are bigger and they can easily block access to a memory slot.
The next step is to install a 92 mm or even a 120 mm fan inside your case (rear one) working as an exhaust air fan system.
Anyway, with stock fan I wouldn't run Prime95 at 66 ºC. You will pass week by week cleaning the dust of your CPU because it will go slower.

Thanks, pepe.

Prime95 does seem to be stable. (How would I tell? It seems to be giving normal results.)

Now here's another twist. The 66C temperature I reported is based on the "CPU" listing in the program CPUID Hardware Monitor. However, further down the program window there are also separate listings for each core (1, 2, 3, 4) that never exceed 47C. So I'm confused -- I thought that the four cores WERE what we call the CPU, so how can their individual temperatures be lower than that for the whole? :confused: And which temperature listing should I be monitoring -- the one that reaches 66C, or the ones that get to only 47C?

Rodrigo

[QUOTE=Rodrigo;256445]Thanks, pepe.

Prime95 does seem to be stable. (How would I tell? It seems to be giving normal results.)

Now here's another twist. The 66C temperature I reported is based on the "CPU" listing in the program CPUID Hardware Monitor. However, further down the program window there are also separate listings for each core (1, 2, 3, 4) that never exceed 47C. So I'm confused -- I thought that the four cores WERE what we call the CPU, so how can their individual temperatures be lower than that for the whole? :confused: And which temperature listing should I be monitoring -- the one that reaches 66C, or the ones that get to only 47C?

Rodrigo[/QUOTE]
What's likely happening here is that the CPUID Hardware Monitor is not reading your CPU's sensors properly. This is unfortunately a common phenomenon because each motherboard has a slightly different sensor interface. You thus have to take a sort of educated guess as to which one is "correct". In your case, I'd say that the 66C temperature is correct, since 47C would be remarkably low for a typical modern CPU with a stock cooler residing next to a graphics card. (Regarding individual cores, yes, they can have different temperatures, though they usually stay close together. In your case, those separate listings are [I]supposed[/I] to be displaying each core's temperature, though they would appear to be reading incorrectly here.)

Note that even the 66C temperature may not be precisely correct; quite often, different temperature-monitor programs will read a particular CPU differently. They will, however, be consistent with themselves and roughly in the correct vicinity. As an example, Core Temp on my Core 2 Duo E4500 reads a temperature of (for instance) 81C with a reported TJunction Max of 85C; yet Real Temp reads 86C at the same time and reports TJunction Max at 90C. In this case, Real Team is ironically the incorrect one; Intel gives the TJunction Max as 85C. So one program's reading will often differ from another's, but they will always be consistent with themselves relative to their reported TJunction Max. By looking at the different reported Tj. Max figures, you can determine how to equate readings from different programs; and if you know what the manufacturer's stated Tj. Max is, you can figure out which program is "right". (Recall that the 71C you read earlier as a "maximum" figure is only the thermal spec, not the Tj. Max; AMD may have that one posted somewhere, but then again they may not necessarily, in which case you'll just have to rely on the relative measurements, which are good enough for preventing your CPU from exploding. :smile:)

mdettweiler,

Thanks for another detailed roundup!

I'll see if I can track down the TJunction Max for that CPU. I'll also check out SpeedFan and one or two other temperature monitors, and see how their readings compare to the CPUID HWMonitor.

Much appreciated.

Rodrigo

mdettweiler,

OK, I installed PC Wizard and SpeedFan on the new PC. They both report the same info as the CPUID HW Monitor -- 65-66C for the "CPU," and 47-48C for each of the "cores."

What do you think?

BTW, I couldn't find TJunction Max information for the Athlon II X4 640. Searched under that, under Tj max, under Thermal Junction max -- no dice. Maybe I'm not looking in the right places.

Rodrigo

[QUOTE=Rodrigo;256524]mdettweiler,

OK, I installed PC Wizard and SpeedFan on the new PC. They both report the same info as the CPUID HW Monitor -- 65-66C for the "CPU," and 47-48C for each of the "cores."

What do you think?[/quote]
Given that multiple programs are reading the same thing, I'd hazard a guess that the 65-66C figure is on the ball relative to what AMD intended. You may want to try Core Temp and RealTemp as well (try Googling them)--I know for a fact that they both use different methods for detecting temperature, so usually one or the other will produce the correct temperature (and the other will be off by a fixed amount).

Do SpeedFan and/or PC Wizard report what they're reading as the TJunction Max? (Some programs will also display it as a "delta to Tj. Max", i.e. the difference of Tj. Max and the current temperature.)

[quote]BTW, I couldn't find TJunction Max information for the Athlon II X4 640. Searched under that, under Tj max, under Thermal Junction max -- no dice. Maybe I'm not looking in the right places.

Rodrigo[/QUOTE]
Have you tried AMD's website? That's the one place that should have it, if anyone does. There's still a chance though that AMD does not publish the Tj. Max; from what I've seen, their website is not as well organized as Intel's and doesn't have as much information easily available. I recall that they usually give the thermal spec, but not necessarily the Tj. Max.

If you can't find the Tj. Max anywhere, that's still OK; even though you won't know absolutely for sure which temperature-sensor program is correct, they should all be correct within themselves relative to what they see as the Tj. Max. In other words, they should all give the correct "delta to Tj. Max", which is enough to be confident that the system is not in danger of a thermal shutdown (well, perhaps "danger" isn't the right word...it's not going to harm your computer, but an improper shutdown of any kind can be a big pain in the butt if you're doing something at the time :smile:).

[QUOTE=mdettweiler;256527]Have you tried AMD's website? That's the one place that should have it, if anyone does. There's still a chance though that AMD does not publish the Tj. Max; from what I've seen, their website is not as well organized as Intel's and doesn't have as much information easily available. I recall that they usually give the thermal spec, but not necessarily the Tj. Max.
[/QUOTE]
mdettweiler,

You weren't kidding about AMD's website! It's a chaotic mess -- hard to find what you're looking for. And they themselves seem to be at best dimly aware that their company has a 640 version of that chip.

Anyway, I did find what seems to come closest to specs for this chip on their site, and you're right, there's no mention of the Thermal Junction Max or any variation of that name (none that I could find, anyway).

Nor does either PC Wizard or SpeedFan give a reading that's obviously related to Tj max.

I'll give RealTemp and CoreTemp a try and report back, thanks!

Rodrigo

mdettweiler,

OK, I downloaded CoreTemp and it's reporting TjMax at 70C, and the CPU temperature at 46C (Prime95 running).

The latter value matches the readings for the [U]individual[/U] cores given by SpeedFan, PC Wizard, and CPUID HW Monitor. We're still left to deal with the 66C CPU readings given by these other programs.

What do you think?

Rodrigo

P.S. RealTemp -- Unfortunately, according to their website it's for Intel processors only.