I have created a VM image out of a physical PC running Windows XP. I am now trying to run that image as a guest OS under Ubuntu Linux using VirtualBox. Everything seems to be running smoothly with the exception of one issue:

The performance of the guest OS is extremely slow, and it shows extremely high CPU usage to complete even simple tasks like opening up a dialog box.

One thing that I have noticed is that when I right click on "My Computer" and go to "Properties" in the guest OS, it shows the CPU information as follows:

Pentium (D) CPU 2.80Ghz 3.95Ghz, 896MB RAM

Now the intriguing part here is that the Pentium D 2.8Ghz processor is what the host machine is running, but I have no idea what the 3.95Ghz is about. I should also note that the 3.95Ghz during a previous boot of the image read something along the lines of 5.2Ghz!

I'm thinking there is a processor issue here. Does anyone have a solution? I have already tried uninstalling the processor in the Device Manager and rebooting, which didn't fix it.


I've had a similar issue and had to use the 'taskset' tool to set the affinity for CPU0; it appears a number of folks have the same problem. Here's a concise artticle:


On my system I did it a little more directly than 'taskset -c 1' as they list; I found the direct command in the process list that launches the exact VM I want (which includes the VM's unique SID) and created a simple helper script to run it, like so:

/bin/taskset 0x00000001 /usr/lib/virtualbox/VirtualBox -comment WindowsXP -startvm a7487a75-6119-4a14-a8ea-195ce2906a4b &

This was on Fedora, the Ubuntu paths might be a slight bit different so adjust as necessary.


"Pentium (D) CPU 2.80Ghz" is the processor name passed by the hypervisor (via cpuid), "3.95Ghz" is the estimated frequency computed by the guest. The calibration routine is probably confused by the virtualization... if the guest is using TSC for calibration and the host CPU does not have synchronized TSCs between cores then from guest POV the TSC will tick at an incorrect rate (it could even go backward); the Pentium D have synced TSCs. so the problem is elsewhere... SpeedStep probably (the host changes CPU frequency and the guest is not aware of the change).

Are you running the latest version of VBox?

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