Alex wrote: /dev/hpet didn't quite work in kernels before about 2.6.15 because of various bugs. The example program uses a kernel header that probably isn't available to user space programs. And if you got it to compile, it probably wouldn't run because the third timer is the only one available (the first two are used for the system timer and for RTC emulation, respectively), and most BIOSes don't initialize the third interrupt. When HPET is enabled, gettimeofday() uses it. What is the output of "dmesg | grep -i hpet"? If you want to avoid the syscall overhead, you can try to call mmap() on /dev/hpet and read the timer directly. In that case, you don't need to use any header. HTH Clemens