How room temp. affects processor temp. (graphs)

[graysky]

I was curious just how much room temperature can affect the temperature of the PC. I chose to look at the CPU since Speedfan can monitor and log temps for each of the 4 cores in my Q6600, and since of all the components, the CPU is probably the most sensitive to changes in air temp. since mine is air cooled.

Anyway, I did the same x264.exe encode that I have been doing for all my temperature comparisons and monitored room temp. with a calibrated digital thermometer at several points during each encode. These were averaged and graphed against the averaged reported core temp* values from Speedfan for the entire second pass of a 2-pass x264 encode of the same video file. I was happy to see that for the different room temps used, the increases were pretty linear (certainly within error).

Result:
You can see by the slopes of the regression line that every delta °F of room temp. affected the average core temp by about 0.8 °C and for your Celsius folks, every delta °C of room temp. affected the average core temp by about 1-1/2 °C.

So what does this mean and why do you care? Well, using these rules of thumb, if it's currently 70 °F in your room, and your average load core temp is 65 °C, you can expect that to change by roughly 0.8 °C for every single °F your room temp. change. Say your room hits 80 °F. Your load core temp should increase from 65 to 73 °C which may be unacceptable to you and you might want to adjust your o/c accordingly. This is just an approximation based on my system. Your mileage may vary...

*The numbers I used are equivalent to those collected by TAT or RMClock: these temps are core temps. As I understand it, TJunction never changes and is a fixed value for a given chip. The Quads get a values of 100 °C and the duals get 85 °C. The core temp is defined as:

Core temp = TJunction - DTS

Example, DTS reads 62.  You take 100-62=38 and your core temp is 38 °C.

DTS (Digital Thermal Sensor) can be read directly for each core. See this thread for more on reading your DTS directly without software like TAT or RMClock paying attention to uncleweb's posts using crystalCPUID to read the DTS directly. When I tried this method, I was able to get the same values for the core temps on my Q6600 as TAT and RMClock gave me. For some reason, Speedfan always shows cooler core temps for my chip which I corrected by adding 15 °C to each temp (the table is CORRECTED temps). Read more about that in the caption under the graph.

Raw data and graphs
Hardware specs: Q6600 (lapped) @ 9x333, Ultra-120 Extreme (lapped), P5B-Del., P182 case w/ 4 fans on low, Corsair 620HX, Ballistix DDR2-800 @ 4-4-4-12 (1:1 Mem:CPU).



Raw data table in case you want the individual points:



Downloads and References
To download crystalCPUID: http://crystalmark.info/software/Cry...D/index-e.html
To download rmclock: http://cpu.rightmark.org/products/rmclock.shtml
To download speedfan: http://www.almico.com/speedfan.php
To download TAT: http://www.techpowerup.com/downloads/392/mirrors.php

To read more about TJunction and for a discussion about other things relating to thermal output fromC2D chips, see: http://forumz.tomshardware.com/hardw...topic&t=221745

[Renfield]

Useful information, thanks for caclulating it out!
I notice from your specs you have the fans on low. Is there any chance you could repeat it with variable speeds to calculate how a delta Fan RPM affects the room:CPU temp ratio?
Thanks either way.

[jas420221]

Wow great job!!!

[Andrew LB]

Good info. The rise in component temps are definitely not proportional to the ambient temps in the room from what I've seen. Right now my E6600 @ 3.4ghz is idling at 30'c while earlier this week when we had that heatwave here in Southern California, it would idle around 42'c.

I don't have a way of reading temperature in my room which is the warmest of the house since my computer is like a space heater but I know that outside about 1/2 mile away at the Seal Beach Naval Weapons Station is only 16'c. (it's only 9:40am and slightly overcast)

[apexracing]

This is good info for anyone interested. Room temperature makes a huge difference in CPU temps. My X2 runs 3-4c hotter on load in just a slightly warmer room.

[NickS]

Heh, I saw you post this at Anandtech.. and I replied with;

It's pretty much common sense. As ambient warms, so will everything else.. 1:1.

I guess this clears it up for some people though.

Hehe..

[graysky]

I notice from your specs you have the fans on low. Is there any chance you could repeat it with variable speeds to calculate how a delta Fan RPM affects the room:CPU temp ratio?
Thanks either way.

That would be interesting since what you're really measuring in an experiment like that is how efficient your case airflow is... since you can't get cooler than ambient. It takes over 90 minutes per run with the file I'm using (I didn't use the temp data from the first pass though since it only uses about 80 % of the CPUs), and it was actually pretty tedious since I keep coming back to the room to record the temp on the digital thermometer by hand so I could average them. I don't think I'll be repeating this experiment with different case fan speeds, but as it heats up this summer, I'll probably record some higher room temp. results to see if that 1:2 ratio holds true.

Thanks for the interest.

[graysky]

Good info. The rise in component temps are definitely not proportional to the ambient temps in the room from what I've seen. Right now my E6600 @ 3.4ghz is idling at 30'c while earlier this week when we had that heatwave here in Southern California, it would idle around 42'c.

I've seen the same thing. It was about 80 °F in here last week and my idle temps were like 10 °C higher than usual. What would be really cool would be sort of on-demand FSB sort of like what speedstep is to the multiplier for the FSB and the voltage. Maybe AISuite does this, I haven't messed with it.

The goal would be keeping the temps low, for example, if you're just going to be browsing the web or typing, you really don't need your o/c'ed values. I'd use this if I didn't have to reboot and reconfigure my BIOS each time I wanted to switch speeds and voltages.

[graysky]

Glad someone else is finding this useful -- always glad to contribute.

[kingdomwinds]

my room is extremely hot these days and my cpu idles 55c. It used to be in the mid 40s when it was colder.

[graysky]

my room is extremely hot these days and my cpu idles 55c. It used to be in the mid 40s when it was colder.

Dude, that's pretty hot for idle if those are tcase numbers...

Are they tcase or tjunction?
What are the load temps?
What are you cooling it with (HS) and how well ventilated is your case?

[kingdomwinds]

measured with TAT. My case is a centurion 5, which as 80mm intake and 120 exhaust. I use tuniq tower but i think i have bad contact.

So far, i have not had any stability problems but my load temps are 62c-65.

Today, it is not has hot as yesterday. So i am idling 47c right now.

[graysky]

measured with TAT. My case is a centurion 5, which as 80mm intake and 120 exhaust. I use tuniq tower but i think i have bad contact.

So far, i have not had any stability problems but my load temps are 62c-65.

Today, it is not has hot as yesterday. So i am idling 47c right now.

Those temps aren't too bad then but I'll bet you can easily shave off 6-10 °C of your temps by lapping both the CPU and HS. It's not as tough as you think it is was the conclusion I came to after doing it myself for the first time recently.

Here are the links to the threads I started here sharing my experiences with both of them; they have pictures and temp. results:

Q6600 IHS lapping
Ultra-120 Extreme lapping

[falqon]

Heh, I saw you post this at Anandtech.. and I replied with;

It's pretty much common sense. As ambient warms, so will everything else.. 1:1.

I guess this clears it up for some people though.

Hehe..

Someone who things shiney processors somehow help probably would post something like that.

[jas420221]

Someone who things shiney processors somehow help probably would post something like that.

Im going ot give this one the benefit of the doubt and say he was sarcastic before I go and get banned for publically spanking him in front of everyone...

Ahh it...

[CaNNibaL]

yap well done ! now all buy air conditioning

[One_Hertz]

yeah I've noticed it wasnt anywhere near a 1:1 increase a while ago and moved everything to the basement.

[Kaze06]

Window A/C units ftw.

[Spawne32]

So what are you saying here? If my room temperature goes up, so will the temp of my computer?!?!?!

[CaNNibaL]

So what are you saying here? If my room temperature goes up, so will the temp of my computer?!?!?!

yap that's for sure !^^
What he is saying is that when your room temp goes up 1ºC, your cpu's temp will increase 2ºC. In a rate room-cpu of 1-2

Regards

[freecableguy]

Let me give you the truth: A 1 degree rise in ambient will result in a 1 degree rise in core temps. Any discrepancy noted is due to error in measurement (either core temp or room temp, you choose).

[mukmaster]

HMM do you know what I love this guide but I cant change the ambient temps so it is useless. I can alaways change my cooler though !!

[graysky]

Let me give you the truth: A 1 degree rise in ambient will result in a 1 degree rise in core temps. Any discrepancy noted is due to error in measurement (either core temp or room temp, you choose).

Well, I'm no statistician nor am I an Intel engineer, so I can't speak to experimental errors/instrument errors. What I can tell you is that whatever relationship I measured in this experiment gave a pretty tight data set.

@mukmaster - Right, without running an A/C you can't really change your room temp, but you can understand that if the room temp raises 8 °C, you can expect your CPU load temps to increase roughly by 16 °C.

[Spawne32]

Well, I'm no statistician nor am I an Intel engineer, so I can't speak to experimental errors/instrument errors. What I can tell you is that whatever relationship I measured in this experiment gave a pretty tight data set.

@mukmaster - Right, without running an A/C you can't really change your room temp, but you can understand that if the room temp raises 8 °C, you can expect your CPU load temps to increase roughly by 16 °C.

do you even see the problem here with the cpu temp going up by double the increase of the room temp?

[RealTelstar]

yap well done ! now all buy air conditioning

Yes, definitely!
With the summer approaching we need it cool