[StRaNNiK]

This patch adds a CONFIG_HZ option to x86, allowing the kernel- internal HZ to be reduced from 1000 to 512 or 100. This solves lost timer interrupt problems on really old machines like my 486. According to Alan Cox, HZ==1000 is also harmful on some laptops (presumably due to long SMI windows), so this patch should be useful for those too. Selecting a lower HZ may also help thermal efficiency slightly, by allowing machines to idle longer between timer interrupts. HZ==100 also reduces the size of the kernel, since it eliminates a lot of HZ<-->USER_HZ conversions. HZ==512 may or may not be useful, but it does work. Why 512 and not 500? It's to avoid having to correct for HZ != 1<<SHIFT_HZ in kernel/timer.c:second_overflow(). The patch also fixes some jiffies_to_clock_t() buglets, which cause warnings in fs/proc/proc_misc.c when (HZ % USER_HZ) != 0

вот оффициальное описалово