Phoronix: Adaptive Tickless Linux Kernel Support Status
Back in 2007 (the Linux 2.6.21 days) the mainline Linux kernel received tickless idle support. With the system idling, the timer tick no longer needlessly goes off with the "NOHZ" feature. Being worked on since last year is now adaptive tickless support, which extends the tickless functionality to non-idle cases...
I remember, last time I build kernel with NOHZ, the system refused to powerdown, unless I tap on keyboard.. Linux truely uncovers some weird low-level hardware quirks..