For certain purposes it can be useful to accelerate or to slow down the virtual guest clock. This can be achieved as follows:

$ VBoxManage setextradata VM-name "VBoxInternal/TM/WarpDrivePercentage" 200

The above example will double the speed of the guest clock while

$ VBoxManage setextradata VM-name "VBoxInternal/TM/WarpDrivePercentage" 50

will halve the speed of the guest clock. Note that changing the rate of the virtual clock can confuse the guest and can even lead to abnormal guest behavior. For instance, a higher clock rate means shorter timeouts for virtual devices with the result that a slightly increased response time of a virtual device due to an increased host load can cause guest failures. Note further that any time synchronization mechanism will frequently try to resynchronize the guest clock with the reference clock, which is the host clock if the Guest Additions are active. Therefore any time synchronization should be disabled if the rate of the guest clock is changed as described above. See .