Hi, I noticed tsc is always marked unstable on my box with 2.6.25* , 2.6.24 is fine. ... [ 0.825760] ACPI: PCI Interrupt 0000:03:0e.0[A] -> GSI 22 (level, low) -> IRQ 22 [ 0.805755] Switched to high resolution mode on CPU 1 [ 0.794244] Switched to high resolution mode on CPU 2 [ 0.766968] Switched to high resolution mode on CPU 3 [ 1.083944] Switched to high resolution mode on CPU 0 [ 15.388792] Clocksource tsc unstable (delta = 9373391604 ns) [ 15.714648] Time: acpi_pm clocksource has been installed. ... Booting nohz=off fixes that. Another strange thing is when I try to boot that kernel with clocksource=acpi_pm it just hangs. config is attached. Please let me know if you need more infos / want me to try patches or anything else. Regards, Gabriel