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#1 2013-03-28 17:08:28

CheesyBeef
Member
Registered: 2008-06-04
Posts: 190

CPU idles much cooler in Arch than Windows 7/8?

Strangely, I've noticed that my CPU idles much cooler in Arch Linux than Windows 7/8. I've been testing in both operating systems at near 0% CPU usage (idle). In both Windows 7 and 8, my CPU idles at around 36-38 degrees Celsius. In Arch, my CPU idles much lower at around 28-29 degrees Celsius - a drop of 8-9 degrees!

Short of any "cuz M$ sucks" comments, does anyone know why this is occurring? 36-38 degrees certainly isn't a bad idle temperature, but I'm wondering why there's such a big difference. I've searched Google and it seems most people have the opposite problem - the CPU runs hotter in Linux than Windows.

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#2 2013-03-28 18:52:03

andmars
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Registered: 2012-03-13
Posts: 153

Re: CPU idles much cooler in Arch than Windows 7/8?

And have you compared the fanspeed, too? Do your fans run at the same rounds per minute as well? Maybe the fans run slower in Windows than in Linux and allow a higher temperature. Appart from that: which desktop-environment or window-manager do you use in Arch? Of course your cpu/gpu has less workload if you run Linux with a minimal setup and a tiling-window-manager than it has in Windows 7/8 with all effects on. Oh, and M$ sucks btw ;-)

Last edited by andmars (2013-03-28 19:24:07)

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#3 2013-03-28 19:29:23

blackout23
Member
Registered: 2011-11-16
Posts: 780

Re: CPU idles much cooler in Arch than Windows 7/8?

I would consider 36-38 C° a strangely high idle tempearture assuming your ambient temperature is about 20 C°.

Could be on Windows something draws CPU cycles. The CPU % load might not be the best indicator for that. Just my guess.

Last edited by blackout23 (2013-03-28 19:29:48)

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#4 2013-03-28 20:41:35

nomorewindows
Member
Registered: 2010-04-03
Posts: 2,956

Re: CPU idles much cooler in Arch than Windows 7/8?

Are you reading all of your thermal inputs correctly?  There maybe several of them, and may not be consistent between linux and windows.
Windows 7 started to be smart about applications reducing the all run time of the cooling fan thus defeating the purpose of a idle fan speed.
Linux is controlled by how the applications are open and what they are doing, which is essentially what windows does, but it has to program in the efficiencies so that the fan will not have any reason be running.


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#5 2013-03-29 01:41:18

anonymous_user
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Registered: 2009-08-28
Posts: 3,058

Re: CPU idles much cooler in Arch than Windows 7/8?

Which program(s) (for both Windows and Linux) are you using to read the temperatures? And which processor do you have?

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#6 2013-03-29 02:08:33

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 12,392

Re: CPU idles much cooler in Arch than Windows 7/8?

blackout23 wrote:

I would consider 36-38 C° a strangely high idle tempearture assuming your ambient temperature is about 20 C°.

I would assert a 15-20°C rise is temperature is rather nominal, if not low hmm
I find it hard to hard to believe one would see less than a 10° rise.

I suppose we could be mixing apples and oranges here.  Any chance that on Windows you are instrumenting the junction temperature of the CPU, whereas is Linux you are instrumenting the exhaust air temperature, or perhaps the heatsink temperature?


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Like you, I have no idea what you are doing, but I am pretty sure it is wrong...Jasonwryan
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#7 2013-03-29 02:58:09

CheesyBeef
Member
Registered: 2008-06-04
Posts: 190

Re: CPU idles much cooler in Arch than Windows 7/8?

My computer has two types of CPU temperature sensors. My Asus motherboard has a CPU temperature sensor that I believe measures from the surface of the CPU. My AMD Phenom II 965 CPU also has built in core temperature sensors that measure from inside the CPU (I was referencing these core temps in my original post).

For the CPU core temperatures, I am using the k10temp lm_sensors module on Linux and AMD Overdrive on Windows. But I have also used several other Windows utilities to verify that AMD Overdrive is using the same temperature source. I don't know of any other utilities on Linux to verify that k10temp is accurate.

For the Asus motherboard CPU temperature, I am using the Asus atk0110-acpi lm_sensors module on Linux and the Asus AI Suite on Windows.

Both the motherboard CPU temp and CPU core temps are lower on Linux than Windows.

Are there any other temperature monitoring utilities than lm_sensors to verify the CPU core temperatures on Linux?

Last edited by CheesyBeef (2013-03-29 03:19:04)

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#8 2013-03-29 02:59:30

anonymous_user
Member
Registered: 2009-08-28
Posts: 3,058

Re: CPU idles much cooler in Arch than Windows 7/8?

BTW you should check what temps you get while just in BIOS.

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#9 2013-03-29 03:08:57

CheesyBeef
Member
Registered: 2008-06-04
Posts: 190

Re: CPU idles much cooler in Arch than Windows 7/8?

anonymous_user wrote:

BTW you should check what temps you get while just in BIOS.

My CPU has always seemed to run hotter in BIOS than anywhere else. But I went ahead and checked. I rebooted from Linux, where my temp was about 31 degrees Celsius, and went straight into the BIOS. In BIOS, the temperature started at 34 degrees and rose up to 38 degrees relatively quickly and stayed there. The fact that it started at 34 degrees tells me that the Linux temperature must hold some sort of validity.

Edit: I tried rebooting from Windows, where my temp was about 38 degrees, and started up the BIOS. Contrary to what happened with Linux, the temp in BIOS started out at 38 degrees and stayed there.

Last edited by CheesyBeef (2013-03-29 03:16:11)

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#10 2013-03-29 10:17:32

blackout23
Member
Registered: 2011-11-16
Posts: 780

Re: CPU idles much cooler in Arch than Windows 7/8?

ewaller wrote:
blackout23 wrote:

I would consider 36-38 C° a strangely high idle tempearture assuming your ambient temperature is about 20 C°.

I would assert a 15-20°C rise is temperature is rather nominal, if not low hmm
I find it hard to hard to believe one would see less than a 10° rise.

I suppose we could be mixing apples and oranges here.  Any chance that on Windows you are instrumenting the junction temperature of the CPU, whereas is Linux you are instrumenting the exhaust air temperature, or perhaps the heatsink temperature?

When the CPU is idle and clocked down there is no way it draws so much power that even with half decent cooling you'll get a 20 C° rise.
7-8 C° above ambient temperature is the norm.

My Idle temps:

me@archbox ~ % sensors
acpitz-virtual-0
Adapter: Virtual device
temp1:        +27.8°C  (crit = +99.0°C)
temp2:        +29.8°C  (crit = +99.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +29.0°C  (high = +80.0°C, crit = +98.0°C)
Core 0:         +29.0°C  (high = +80.0°C, crit = +98.0°C)
Core 1:         +28.0°C  (high = +80.0°C, crit = +98.0°C)
Core 2:         +29.0°C  (high = +80.0°C, crit = +98.0°C)
Core 3:         +29.0°C  (high = +80.0°C, crit = +98.0°C)

The values I get from lm_sensors are exactly the same as in Windows with RealTemp also under load.

Last edited by blackout23 (2013-03-29 10:28:44)

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#11 2013-03-30 00:57:04

cfr
Member
From: Cymru
Registered: 2011-11-27
Posts: 5,661

Re: CPU idles much cooler in Arch than Windows 7/8?

I never get anything much below the mid-40s:

$ sensors
acpitz-virtual-0
Adapter: Virtual device
temp1:        +44.0°C  (crit = +100.0°C)

thinkpad-isa-0000
Adapter: ISA adapter
fan1:         567 RPM
temp1:        +44.0°C  
temp2:         +0.0°C  
temp3:        +44.0°C  
temp4:         +0.0°C  
temp5:         +0.0°C  
temp6:         +0.0°C  
temp7:        +23.0°C  
temp8:         +0.0°C  

coretemp-isa-0000
Adapter: ISA adapter
Physical id 0:  +47.0°C  (high = +86.0°C, crit = +100.0°C)
Core 0:         +46.0°C  (high = +86.0°C, crit = +100.0°C)
Core 1:         +46.0°C  (high = +86.0°C, crit = +100.0°C)

Ambient temperature will be below 20C at this point. I seem to get higher RPM when laptop is cooler...


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#12 2013-03-30 01:37:30

ewaller
Administrator
From: Pasadena, CA
Registered: 2009-07-13
Posts: 12,392

Re: CPU idles much cooler in Arch than Windows 7/8?

blackout23 wrote:

When the CPU is idle and clocked down there is no way it draws so much power that even with half decent cooling you'll get a 20 C° rise.
7-8 C° above ambient temperature is the norm.

T sub J = T sub A + [ R sub (θJA) × P sub D ]

Where:
T sub J = The junction temperature.
T sub A = Ambient Temperature.
R is the thermal resistance.
P sub D is the dissipated power in the processor.

Thermal resistance for a BGA package with a heatsink and forced convection is on the order of 15 degrees C per Watt.

So your processor idles around 500mW, mine, just over 1.3 ( 20/15).

Modern Intel processors draw on the order of 30 W at full power and (by the book) on the order of 1 W at idle.
I would say you are low,and I am high.


Nothing is too wonderful to be true, if it be consistent with the laws of nature -- Michael Faraday
Like you, I have no idea what you are doing, but I am pretty sure it is wrong...Jasonwryan
----
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#13 2013-03-30 01:49:13

the sad clown
Member
From: 192.168.0.X
Registered: 2011-03-20
Posts: 833

Re: CPU idles much cooler in Arch than Windows 7/8?

ewaller wrote:

Thermal resistance for a BGA package with a heatsink and forced convection is on the order of 15 degrees C per Watt.

That sounds right to me.  My idle temp is usually mid to upper 30's.  I don't think I've ever seen it in the 20's unless the ambient temp is significantly lower than 20C.

Last edited by the sad clown (2013-03-30 01:51:32)


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#14 2013-03-30 12:52:35

nomorewindows
Member
Registered: 2010-04-03
Posts: 2,956

Re: CPU idles much cooler in Arch than Windows 7/8?

ewaller wrote:
blackout23 wrote:

When the CPU is idle and clocked down there is no way it draws so much power that even with half decent cooling you'll get a 20 C° rise.
7-8 C° above ambient temperature is the norm.

T sub J = T sub A + [ R sub (θJA) × P sub D ]

Where:
T sub J = The junction temperature.
T sub A = Ambient Temperature.
R is the thermal resistance.
P sub D is the dissipated power in the processor.

Thermal resistance for a BGA package with a heatsink and forced convection is on the order of 15 degrees C per Watt.

So your processor idles around 500mW, mine, just over 1.3 ( 20/15).

Modern Intel processors draw on the order of 30 W at full power and (by the book) on the order of 1 W at idle.
I would say you are low,and I am high.

I guess that means that laptops don't do so hot.  Mine's always jumping around to 60C everytime the processor sneezes.  Any intensive task such as virtualization, will make it easily hit 70C (does not have VT-x).


I may have to CONSOLE you about your usage of ridiculously easy graphical interfaces...
Look ma, no mouse.

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#15 2013-03-30 20:48:44

na12
Member
From: /home/serbia
Registered: 2008-12-23
Posts: 749

Re: CPU idles much cooler in Arch than Windows 7/8?

On my HP laptop I get the same thing,lower temperature on Linux than Windows 7/XP,about 5 degrees celsius.

Last edited by na12 (2013-03-30 20:49:09)

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#16 2013-03-30 23:15:44

brebs
Member
Registered: 2007-04-03
Posts: 3,406

Re: CPU idles much cooler in Arch than Windows 7/8?

andmars wrote:

And have you compared the fanspeed, too? Do your fans run at the same rounds per minute as well?

CheesyBeef, you still haven't answered this.

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#17 2013-04-01 05:17:20

CheesyBeef
Member
Registered: 2008-06-04
Posts: 190

Re: CPU idles much cooler in Arch than Windows 7/8?

brebs wrote:
andmars wrote:

And have you compared the fanspeed, too? Do your fans run at the same rounds per minute as well?

CheesyBeef, you still haven't answered this.

Sorry, yes the fan speed is dynamically controlled by my motherboard and is approximately the same in both operating systems. Even when I override the fan speed to maximum in Windows, it does not noticeably lower the idle temperature.

@na12 - Interesting to hear someone else is experiencing this as well and it's not just me. By the way, what is your CPU in that laptop?

Last edited by CheesyBeef (2013-04-01 05:19:41)

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#18 2013-04-01 07:48:49

t1nk3r3r
Member
From: The Pacific Northwest
Registered: 2011-03-22
Posts: 79

Re: CPU idles much cooler in Arch than Windows 7/8?

This may or may not have bearing, but a quote of a quote:

There is one temperature measurement value, available as temp1_input in
sysfs. It is measured in degrees Celsius with a resolution of 1/8th degree.
Please note that it is defined as a relative value; to quote the AMD manual:

  Tctl is the processor temperature control value, used by the platform to
  control cooling systems. Tctl is a non-physical temperature on an
  arbitrary scale measured in degrees. It does _not_ represent an actual
  physical temperature like die or case temperature. Instead, it specifies
  the processor temperature relative to the point at which the system must
  supply the maximum cooling for the processor's specified maximum case
  temperature and maximum thermal power dissipation.

The maximum value for Tctl is available in the file temp1_max.

kernel Documentation/hwmon/k10temp


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#19 2013-04-01 14:09:46

na12
Member
From: /home/serbia
Registered: 2008-12-23
Posts: 749

Re: CPU idles much cooler in Arch than Windows 7/8?

CheesyBeef wrote:

@na12 - Interesting to hear someone else is experiencing this as well and it's not just me. By the way, what is your CPU in that laptop?

┌╸dany╺─╸~╺
└─╍ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                2
On-line CPU(s) list:   0,1
Thread(s) per core:    1
Core(s) per socket:    2
Socket(s):             1
NUMA node(s):          1
Vendor ID:             AuthenticAMD
CPU family:            15
Model:                 104
Stepping:              1
CPU MHz:               800.000
BogoMIPS:              1596.49
Virtualization:        AMD-V
L1d cache:             64K
L1i cache:             64K
L2 cache:              512K
NUMA node0 CPU(s):     0,1

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