Messages in this thread | | | Date | Tue, 12 Jul 2005 09:02:42 -0400 (EDT) | From | "Richard B. Johnson" <> | Subject | Re: i386: Selectable Frequency of the Timer Interrupt |
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On Tue, 12 Jul 2005, Jan Engelhardt wrote:
> Hi, > > > Vojtech Pavlik @ Tue, 12 Jul 2005 14:10:08 +0200 wrote: > (http://lkml.org/lkml/2005/7/12/122) > >> On Mon, Jul 11, 2005 at 05:38:05PM -0700, George Anzinger wrote: >>> HZ TICK RATE jiffie(ns) second(ns) error (ppbillion) >>> 100 1193180 10000000 1000000000 0 > >> The PIT crystal runs at 14.3181818 MHz (CGA dotclock, found on ISA, ...) >> and is divided by 12 to get PIT tick rate >> 14.3181818 MHz / 12 = 1193182 Hz > > What exactly is the frequency of the PIT? Many internet resources say 1193180 > (including the original post), some say 1193181, and you say 1193182 Hz. > Which one is correct? (Ignoring temperature for now..) >
The original specification was based upon the NTSC color subcarrier frequency of 3.579545. The dotclock is 4 times this:
3.579745 * 4 = 14.31818000
You can type 3.579545 into google and see it's used practically everywhere as the magic number that started it all ;^) The crooked-earth society uses this for PI (just kidding).
> IMO 1193181 could be, because it matches the almost-magical number 0x1234DD. > > > Jan Engelhardt > -- > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
Cheers, Dick Johnson Penguin : Linux version 2.6.12 on an i686 machine (5537.79 BogoMips). Notice : All mail here is now cached for review by Dictator Bush. 98.36% of all statistics are fiction. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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