Hi, I tried to time events inside the kernel in 2.4.0test12: Basically the same code works fine in 2.2.18 with about 1us jitter. However in 2.4.0test12 the jitter is around 600ms! What I did is this: I modified the interrupt routine of the serial driver to get a precision time-stamp via do_gettimeofday(). So I guess either interrupts are delayed significantly from time to time, or the time routine has been changed to be no longer useful within interrupt routines. If anybody can enlighen me on this, I'd be happy. I'm not subscribed to linux-kernel, so maybe please CC: Regards, Ulrich - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] Please read the FAQ at http://www.tux.org/lkml/