The TSC does not run at a precisely specified rate, so the guest operating system has to measure its rate at boot time, and this measurement is always somewhat inaccurate. The ACPI PM timer does run at a precisely specified rate but is slower to read than the TSC.
gnawux
commented
7 years ago
The TSC does not run at a precisely specified rate, so the guest operating system has to measure its rate at boot time, and this measurement is always somewhat inaccurate. The ACPI PM timer does run at a precisely specified rate but is slower to read than the TSC.