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Effect of room temp on your CPU load temps

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graysky

Member
Joined
May 6, 2007
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:
Code:
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).

tempsnewcu7.gif


Raw data table in case you want the individual points:

tempsdatatablerb5.gif


Downloads and References
To download crystalCPUID: http://crystalmark.info/software/CrystalCPUID/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
 

E4300

Member
Joined
May 2, 2007
I admit that your alternating use of centigrade and fahrenheit confused me a little. ;)

But recently I did a poll about this in this same forum. I had noticed that my core temperatures for the rig in my sig is always 11 degrees centigrade higher than the room temperature, whatever the room temperature happened to be, and I was curious as to whether you guy's idle core temperatures always were a fixed number above room temperature.

So far I have only monitored the idle temperatures of the cores, using coretemp 0.95. I have also concluded that my tjunction is 100 degrees centigrade - coretemp 0.94 (which assumes tjunction of 85 degrees) states my idle temperature as being 5 degrees below room temperature, which would be impossible unless my cpu's got a minute airconditioner within itself :D.

At 28 degrees room temperature I get an idle of 39 and a load which varies between 61 and 63 on coretemp 0.95.

A couple of weeks ago at 24 degrees room temperature I used to get 35 degrees idling and 58 degrees on 100% load using Orthos.

Edit: Today the room temperature is 32 degrees and I'm idling at 43 degrees core temperatures!
(Measured using coretemp 95. In the Bios the cpu temperature is also 32 degrees, and in Everest ultimate it is... 22 degrees :rolleyes: with both cores at 31 degrees).
 
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cozmo_d

Member
Joined
Dec 21, 2000
Location
Planet X
Its 22 degree Celsius = 71.6 degree Fahrenheit in my room right now.

System is 39 degree Celsius = 102.2 degree Fahrenheit

CPU Core is 41 degree Celsius = 105.8 degree Fahrenheit

no load except this web page

that seems ok to me would like the room cooler but LOL cant afford to pay the man & the gas man :confused:

nice data btw !

PS OC IS NOT APPLIED RIGHT NOW.
 
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Oc1Kenube

Member
Joined
Mar 5, 2007
All i know is in winter i can hit 400fsb with my oc and in summer im struggling to hit 370
 

cozmo_d

Member
Joined
Dec 21, 2000
Location
Planet X
yup im a winter ocer too Id rather run at default in the heat

plus theres lots of stuff to do outside during summer:cool:
 

xsoulbrothax

Registered
Joined
Jan 27, 2003
Location
San Jose, CA
I'm also noticing that my room temperature pretty much slowly but surely creeps up as long as the computer itself is on, especially after the 8800 went in. Sucks!

The CPU seems to idle at less than 10C over ambient, but it's hard to get a good read on what my ambient temps actually are.. the 8800 was reading them at 50C when it got hot in here, and I KNOW that wasn't true. :D Maybe in the case air down where the card is..
 
OP
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graysky

Member
Joined
May 6, 2007
Dunno man, how large is your room? All the heat your CPU/GPU and other components in that case is producing has to go somewhere. Your monitor also produces heat. If the room is small enough, a temp increase from the PC is totally reasonable.
 

xsoulbrothax

Registered
Joined
Jan 27, 2003
Location
San Jose, CA
graysky said:
Dunno man, how large is your room? All the heat your CPU/GPU and other components in that case is producing has to go somewhere. Your monitor also produces heat. If the room is small enough, a temp increase from the PC is totally reasonable.
Yeah, it's also somewhat depressing that I'm pretty sure there is almost nothing to be done about it on air or unchilled water, short of underclocking and/or undervolting. I figure the processor is generating X amount of heat/energy no matter what you're doing with cooling, so more efficient cooling would just be better at taking X amount of heat and dumping it into the room.

The room is maybe.. 10'x16', guessing from a visual look.
 
OP
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graysky

Member
Joined
May 6, 2007
xsoulbrothax said:
The room is maybe.. 10'x16', guessing from a visual look.

Short of getting a small window A/C unit, you can't beat the laws of physics.
 

xsoulbrothax

Registered
Joined
Jan 27, 2003
Location
San Jose, CA
graysky said:
Short of getting a small window A/C unit, you can't beat the laws of physics.
Done. :D I ganked a portable A/C unit (that seems to be a power-hungry beast), and it's currently sitting next to my bed. I leave the comp in standby when I'm not home, and turn it on when the comp goes on during the early hours of the afternoon. It goes off around 5, when the outside air is no longer 90something. The processor is idling in the low 30's again!
 

Hazaro

Member
Joined
Apr 25, 2007
So it looks like a practically 1:1 ratio for ambient and core temp? That's really surprising.
 

CompuTamer

Member with Some Fancy Text Under His Name
Joined
Jan 4, 2009
Location
Brandon Mississippi
My i7 runs pretty warm OCed at idle due to the voltage always being so high.

That being said, it caps at about 78C load, so i'm happy. My laptop can EASILY break 85C outside though... 100F doesn't get along with laptops well at all. In a 74F room, it doesn't even hit 65C under load.