Scott Hanselman

Windows task manager shows wrong CPU Speed when using Hyper-V

April 11, 2013 Comment on this post [21] Posted in Bugs | Tools
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My buddy Damian and I both recently bought the Lenovo X1 Carbon Touch. It's got Intel SpeedStep technology so it changes the CPU speed dynamically based on load. These two laptops of ours are identical. However, here's Damian's Task Manager when mostly idle.His speed is 0.60 GHz

Here's mine.

His speed is 2.49 GHz

What the heck is going on? His CPU is reporting 0.60 GHz of a potential speed of 2GHz, indicating that the chip has chilled out. Mine is reporting "full speed ahead!" at a speed that it doesn't even support, 2.49GHz!

We went around and around on this for a while until we realized that I had turned on Hyper-V Virtualization for Windows Phone Development and my Ubuntu VM. He hadn't.

We installed CPU-Z, a low level and very smart CPU utility and got the truth. In fact, both machines are stepping down, but my Kernel is running within the Hypervisor and it's CPU speed is being reported incorrectly to Task Manager. Task Manager is showing the MAX speed, and not the real (Hyper-V virtualized) speed.



NOTE: CPU-Z is lovely but the wrapper that they put around it is evil spyware and you need to really pay attention when you install or you'll end up installing a bunch of toolbars. Be warned.

I hope this helps someone! It wasted 30 minutes of my life.

About Scott

Scott Hanselman is a former professor, former Chief Architect in finance, now speaker, consultant, father, diabetic, and Microsoft employee. He is a failed stand-up comic, a cornrower, and a book author.

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April 11, 2013 6:04

Oh, I spent HOURS trying to get it to work (install speedstep, etc) and gave up. Thanks for this info.


PS. I love my X1 Carbon Touch, great machine
April 11, 2013 7:44
So the actual bug is with Hyper-V then? Did you report this on MS Connect? I'm curious to see what their response will be.
April 11, 2013 7:52
Hey Scott, would you mind reviewing the Carbon Touch soon? I'm close to pulling the trigger on one and would like to know your pros\cons versus other rigs you've used.
April 11, 2013 8:40
Another problem with Hyper-V and CPU-Z is that once you install Hyper-V CPU-Z will be 100% sure your CPU does not have the VT-x extension even if your CPU and BIOS are both operational.

It's not just CPU-Z either - any utility and virtualization software will find VT-x AWOL until you uninstall Hyper-V.

April 11, 2013 10:01
Hi scott

Is this really a bug or is it a feature?


April 11, 2013 11:11
Hi Scott,

I've also noticed the same thing a few month ago on my Asus Zenbook.
Also the disk performance becomes slower after installing Hyper-V.
April 11, 2013 12:36
Or you can download it directly from the CPUID website. There is also a no installation version of CPU-Z.
April 11, 2013 15:07
I had the problem too. But the thing that made me disable Hyper-V is that having the hypervisor prevents the PC to sleep.
Did you also notice that ?
April 11, 2013 21:16
actionthomas - I haven't had any issues with Sleep and HyperV

Peter - Ah, thanks!

Yurly - I haven't seen any speed issues with the disk, but I'll do some tests.

Jeff - Yes, review incoming.
April 11, 2013 21:24
Great to see this info published, it puzzled me when I first started using Hyper-V (years ago)...Two other comments..

1)any utility and virtualization software will find VT-x AWOL until you uninstall Hyper-V.

Of course, you are (Even on the host) running enside a virtualized environment. VT-x is EXTERNAL to that environment, so technically it does NOT exist within the environment...

2)having the hypervisor prevents the PC to sleep.

Considering (up until Win8) this was a server feature, and servers are meant to serve. I didnt find this suprising...

At least those are my views on the two items...interested to hear others...
April 11, 2013 22:40
@David V. Corbin

If you install ESXi on your host (instead of Hyper-V), you will probably that the VT extensions are visible, despite "running inside a virtualized environment." This is why Hyper-V can be run as a VMWare guest, but not the inverse. What I'm trying to say is that you are being a little smug with the "of course." ;-) Hyper-V is good, but even 2012 is playing catch up with VMWare in some areas. Competition is good!
April 11, 2013 23:41
Not a half hour wasted, Scott. Lots of half hours saved by other people, but that is why you wrote this. As someone who generally enjoys looking under the hood and appreciates being told about quick tools for doing so, many thanks!

Thanks also to peterfoldi!

April 12, 2013 0:18
I had the same issue and came to the same conclusion. My answer to someone having the same issue on <a href=">this SuperUser question</a> helps to explain my understanding of why this occurs.
April 12, 2013 1:29
Reminds me of the half hour of my life i wasted trying to figure out why my laptop was maxing out at a measly 600mhz. Answer: hadn't plugged the charger in (power management being helpful). A+ for doziness.
April 12, 2013 2:24

I don't use Task Manager anymore, since Sysinternals Process Explorer is out.
Did you try it? Same problem?

April 12, 2013 9:42
would love to see review on Carbon touch. I am debating between carbon touch vs running windows on Macbook pro.
Carbon touch seems limited by 8 GB RAM and high end macbook pro can go all the way to 16GB so good for virtual especially looking with sharepoint in mind and heard from few folks that sharepoint eats lot of memory. Sahil Malik says in his kindle book on Sharepoint 2013 development machine that "Sharepoint eats RAM for breakfast and fast SSDs for lunch".

Your's / others feedback who own Carbon touch will be highly appreciated.
April 12, 2013 10:07
Gee, for a moment I though I read "Windows Phone Development on my Ubuntu VM"...
April 12, 2013 13:27
No Ethernet or Monitor plugs in this machine? :O
April 12, 2013 15:55
Scott -

Thanks for posting your find with the CPU speed change in task manager after installing Hyper-V in Win8. I have a Gigabyte Mobo and there is USB 3.0 issue that requires me to disable USB 3.0 to install Hyper-V otherwise I get a prompt to have to Refresh my pc which as you can imagine is not preferred (side note: the PC Refresh in Win8 does work good). I am hoping for some additional changes in Hyper-V integration in Win8 to create a smoother experience.
April 12, 2013 23:23
Get rid og HyperV in Windows 8 .. its just rubbish

I've had multiple problems with it, one of them being that my computer couldn't start Windows 8 sometimes, after enabling a Virtual LAN adapter in HyperV

I finally uninstalled HyperV and tried out VmWare Player, which lets your run VM's the same way as VirtualPC for Windows7 - it also enables UnityMode where the client programs can run inside the host OS -- VERY VERY neat if you want to test IE 7-8-9 and old versions of Firefox / Chrome / Opera / Safari.

Or if you need to use Cisco VPN which isn't availble for Windows 8 -- GAAAH ! -- then you simply use a Win7 client to that.

VMWare also runs much smoother than HyperV, and the CPU doesn't work as much.
RAM is also virtual in VMWare, which means that if a client only needs 1.5 GB and you assigned 4 GB, the 3.5 will be free.

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Disclaimer: The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.