Compatibility
Operating systems designed before HPET existed cannot use HPET, so work only on hardware that has other timer facilities. Newer operating systems tend to be able to use either. Some hardware has both. Indeed most current southbridge chips have legacy-supporting instances of PIT, PIC, APIC and RTC devices incorporated into their silicon whether or not they are used by the motherboard or the operating system, which is why even a very modern PC can still run older operating systems.
The following operating systems are known not to be able to use HPET: Windows XP, Windows Server 2003, and earlier Windows versions, Linux kernels prior to 2.6.
The following operating systems are known to be able to use HPET: Windows XP, Windows Server 2008, Windows Server 2008 R2, Windows Vista, Windows 7, x86 based versions of Mac OS X, Linux operating systems using the 2.6 kernel (or later), FreeBSD and OpenSolaris.
Read more about this topic: High Precision Event Timer