[SOLVED] [split] Missing HPET clocksource option

[agent_kith]

To further my findings, with the same CMOS setting, after changing to "TSC" clocksource, the latency becomes as good as before.  huh.... so, with my new NUC, seems the CMOS setting doesn't affect the latency, but the choice of "clocksource".

On some motherboards, I honestly can't discern any notable difference between HPET and TSC. IIRC need to disable hyper-threading.

I believe one is the older technology, and less "accurate" under certain conditions, and the other is meant to be a replacement. If memory serves, HPET is meant to be a replacement for TSC (could be the other way round though ).

And last night, in a second thought, it's quite strange to me that, even in the default CMOS setting, including HPET is enabled, the Snakeoil OS can't use HPET, or the system/hardware can't use HPET with the CMOS default power management setting...... so where is the problem?

HPET is disabled in the kernel. There's apparently some problems with HPET when in C10 mode (power saving mode), so the kernel disables the HPET timer (and falls back to TSC IIRC). So even though HPET is enabled in the system BIOS, the OS will refuse to use it.

If you're using custom kernels, power saving is disabled by default so HPET is always working. Using stock linux kernels, full suite of power saving is enabled hence you may get that missing HPET.