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    SubjectRe: [PATCH] USER_HZ & NTP problems
    On Tue, Sep 10, 2002 at 01:14:49AM +0200, Rolf Fokkens wrote:

    > I've been playing with different HZ values in the 2.4 kernel for a while now,
    > and apparantly Linus also has decided to introduce a USER_HZ constant (I used
    > CLOCKS_PER_SEC) while raising the HZ value on x86 to 1000.
    > On x86 timekeeping has shown to be relative fragile when raising HZ (OK, I
    > tried HZ=2048 which is quite high) because of the way the interrupt timer is
    > configured to fire HZ times each second. This is done by configuring a divisor
    > in the timer chip (LATCH) which divides a certain clock (1193180) and

    Actually, the clock true frequency is 1193181.8 Hz, although most
    manuals say 1.19318 MHz, which, because truncating more digits, also
    correct. But 1193180 Hz isn't. If you're trying to count the time
    correctly, you should better use 1193182 Hz if staying in integers.

    Vojtech Pavlik
    SuSE Labs
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