Windows 8 Hyper-V V3 SpeedStep

tl:dr : zet je Hyper-V aan op Windows8 dan laat taskmanager de juiste cpufrequentie niet meer actief zien.

Running virtual machines on a laptop has always been a consensus between usability and performance. But as IT consultant, Trainer or Developer it’s really handy to have some testvm’s at your fingertips. With Windows 8 you can activate the Hyper-V feature, which enables you to run a bare-metal Hypervisor on a laptop. This makes Windows 8 the perfect choice but…

When I first installed this Windows Hyper-v feature a big showstopper showed up, no more Speedstep. (Intels power saving option) Battery life is important on a laptop and looking into Task Manager and Recource Monitor made me very sad. It seemed to me that Speedstep was not working.

Checking on other Windows 8 and Windows 2012 hyper-v installations confirmed my suspicions: The frequency of the CPU stayed at 100%. Normally frequency throttling would lower the CPU speed and also the corevoltage and would save energy.  In Windows Server 2008R2 these options were still there and working. Best practice was to turn them off in an high performance environment. Was Microsoft finally following the opinion of some engineers, telling that SpeedStep is killing your performance?

Being at TechEd Europe gave me a great opportunity to talk to Microsoft – and Intel specialists about this problem. To them this also looked like an issue. The reply from Microsoft specialists was: “we will email the guy in Redmond”. Back at home I was still puzzling why this was happening. Is this technology so complex and full of errors Microsoft would disable it? I still wanted to use Hyper-V but not without these energy savings disabled.

The solution was simple: What if Taskmanager is looking at a virtualized CPU? When I tried CPU-Z, a well know tool for overclockers, I saw different frequencies and voltages. Now it all became clear to me : The Hypervisor is so great it is also virtualizing the CPU for the parent OS. But under the hood it’s still using energy saving technologies! Windows 8 will definitely become the OS for my laptop.


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