Re: Linux vs Windows temperature anomaly

Ed Sweetman (ed.sweetman@wmich.edu)
Thu, 06 Mar 2003 02:57:31 -0500


This is getting kicked like a deadhorse by now i think but.

Unlike your cpu which gets idle commands from the OS and thus has an
idle loop where it turns off certain circuits and which can get acpi
commands to turn completely off the other chips in the computer do not
have such a luxury. they are always on like the cpus of yesteryear used
to be. It doesn't matter if they have data moving in them or not, no
big difference. The reason why it seems like this is the case is for
you HSF cooled cpu guys, load on the system bus usually means high cpu
load and that means more heat put into the surrounding air and the
little usually passive cooled but regardless, less hot system bus gets
hotter along with the cpu and cooler when the cpu is idle. People
cooled by other methods that do not dump heat into the surrounding air
inside the case will notice that the system bus temp only varies with
ambient air temp changes, not data transfer going on between ram and cpu.

Corvus Corax wrote:
> Am Thu, 6 Mar 2003 10:38:44 +1100
> schrieb Con Kolivas <kernel@kolivas.org>:
>
>
>>That doesn't make sense. His post said the temperature was 20 degrees lower
>>when it failed.
>>
>>Con
>
>
> I think it does,
>
> look at this:
>
> RAM
> ._____________________.
> _|| | | | | | | | | | ||_. ._/| ._/|
> / ||___________________|| |~\ ||/| ||/|
> | |O _____ O| |~\\ /||/| ||/|
> | | .-| | |-. | |\\\\ //|| | || |
> | | / \ |~| | / \ | |\\\\\ //=|| |=|| |
> | | /| |\| |~|/| |\ | |\\\\.________. ///=||/|=||/|
> | | * | | \_._/ |~| * | |\===| |==///==||/|=||/|
> | | |~|~| /CPU\ ~ | | | |====| north |==///==|| |=|| |
> | | | | |~\_ _/ | | | | |====| bridge |=======|| |=|| |
> | | * | | / \ | |~* | |/===| (MEM ) |=======||/|=||/|
> | | \| |/| |~|\|~|/ | |//==| (CTRL) |==\\\==||/|=||/|
> | | \ / |~| | \ / | |////~~~~~~~~==\\\==|| |=|| |
> | | -.|_|_|.- | |///// |||||| \\\=|| |=|| |
> | |O O| |//// |||||| \\=||/|=||/|
> | |~~~~~~~~~~~~~~~~~~~~~| |_// |||||| \\||/| ||/|
> ~|| | | | | | | | | | ||~_/ |||||| \|| | || |
> ~~~~~~~~~~~~~~~~~~~~~ |||||| ||/ ||/
> CPU TEMP | |||||| |_| |_|
> | | voltage ||||||
> | ||| ||||||
> | ||| .________.
> Mainboard | ||| | |
> TEMP .,,,,,,. data | south |
> O | |=======| bridge |
> \\_____'''''' | (BUS ) |
> ~~~~~~ | (CTRL) |
> TEMP & ~~~~~~~~
> VOLTAGE ctrl ////|||\\\\\
> chip PCI & other BUS
>
>
> the sensor for the system temperature (somewhere on the board) is connected to a driver chip (usually on the i2c bus)
> like the w83781d (on my board)
>
> if something now causes the (often badly cooled) bridge to get hot (by more load between some periphery and the RAM for example)
> , the system temperature doesnt necessary have to increase.
>
> if the bridge has only a heatsink, its temperature is somewhat like
> (system TEMP)+ ( produced heatper time / heat given to the air by heatsink per time )
> where the heatsinks capacity is dependent on the delta temperature, too, gets complicated ;)
>
> in short, the chips hotter than the rest of the system and if it has high load it gets even hotter,
> but its temp is still dependant on the main system TEMP. ;)
>
> blahrgh forget what i talk, watch the ASCII art, and imagine the effect of much data running between
> BUS and RAM ;-) (or BUS and BUS if north and southbridge are on the same chip)
>
> CvC
>

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