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How does Win8 keep CPU cooler?

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#16 Fillado



  • Joined: 12-July 05

Posted 13 July 2013 - 10:14

uh, I just tried 4 programs, none of them say the clock speeds went down.  


You might highly doubt that moving from Win7 to Win8 would change temperatures, but you'd be wrong.  Someone else here already confirmed it.  The hardware configuration is the exact same.  My idle temperatures are incredibly consistent, and do not vary by more than 5 degrees over an entire year.  My Win7 idle temp was 39-40*C, every day, for the past 3 months.  Then one day, I installed Windows 8, and my idle temp was 33-34*C, on the very same day that Win7 measured 39-40*C, using the same measuring softwares (I used SpeedFan and OHM on both OSes), which both report that they are getting the data from the same internal sensor ID (IT8720F-1).  


So the only explanations I can think of is that either A) my Win7 install had more CPU usage when idle (very possible, I had a ton of programs installed, but I checked CPU usage often and I would try to eliminate programs that used CPU in the background) than my Win8 install did.  Since I am running the same set of programs on Win8 that I was on Win7, I have to believe that the Windows 8 kernel itself is less CPU-intensive.  This would make sense, since they designed it to be run on battery-powered mobile devices.


or B) the CPU clock speed is being decreased when IDLE, but it isn't being accurately measured by any of the 4 programs I've tried.  Even though they all report the CPU clock speed in real-time, and I can see the minor variations in 100's of kHz in clock speed, so I know that they aren't just a static snapshot of a CPU clock speed in the past.


Well in the new Performance tab of the Windows 8 task manager select CPU and it should be the most accurate thing possible for showing you the current speed. I'd also suggest updating your BIOS as manufacturers will have pushed updates after Windows 8 came out.

#17 Newinko



  • Tech Issues Solved: 1
  • Joined: 27-March 05

Posted 13 July 2013 - 10:46

A processor can be cooler under Windows 8 than under Windows 7 when idle because the system has better idle hygiene than Windows 7, meaning it transitions to idle faster and stays there longer; therefore modern x86 processors such as Intel Cores can go into deeper sleep quicker.


Microsoft made a graph demonstrating Windows 7's vs Windows 8's idle hygiene here:


#18 CJ33



  • Joined: 03-February 03

Posted 13 July 2013 - 18:09

If there's a virus lowering my CPU temp, then that's a damn awesome virus.


or if there is a virus raising your CPU temp on your other setup, then thats damn not awesome

#19 OP moeburn


    tracer bullet

  • Joined: 10-March 04
  • Location: Toronto, Ontario

Posted 22 July 2013 - 00:24

Well it definitely was NOT because of Windows 8 lowering the CPU clock.  I found the ultimate CPU clock monitoring tool: TMonitor - it monitors all core's individual CPU clocks, 20 times per second, and displays them on a graph.  The reason the "minimum processor state" wasn't in the advanced power options dialog, was because AMD Cool 'n' Quiet was turned off in the bios.  Windows simply could not have been, and was not lowering the CPU clocks.  As soon as I turned CnQ on, the "minimum processor" setting was back, and my CPU clocks flew all over the place in TMonitor.  And my idle CPU temp reached 29°c.  That's just 5 degrees above room temp!  Windows 8 just does less in the background when the cpu is idle, because Windows 8 now assumes you are on a battery instead of a desktop pc.  I like it, either way.

#20 vcfan


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Posted 22 July 2013 - 00:38

yep,windows 8 definitely gives you better thermal profiles because its built for this,and low power devices.. like others have mentioned, it idles better, handle hardware devices suspension better, has a new interrupt system,and further optimizations and tweaks to the inner workings of the kernel.

#21 OP moeburn


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  • Joined: 10-March 04
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Posted 22 July 2013 - 00:44

I'm now questioning the effectiveness of AMD Cool 'n' Quiet, though.  I'm running a VNC viewer, which takes a steady 20% of the cpu, according to Task Manager.  Despite that, according to TMonitor, my clocks are still being lowered by CoolnQuiet to 50%.  But my CPU is not running any cooler, or quieter.  SpeedFan still had to raise the fan speed to the usual 60%, because the cpu is still running at 45°c, like it did with CnQ off.  

#22 SharpGreen


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Posted 22 July 2013 - 01:02

Windows 8 groups things that would otherwise wake the CPU (such as timer events and the like), together and runs them in batches instead of just whenever they occur like Windows 7. This allows the CPU to enter its various sleep states more often and stay there longer resulting in cooler operation and less wasted power.