Messages in this thread | | | Date | Thu, 29 Jul 1999 22:06:26 -0400 (EDT) | From | "Albert D. Cahalan" <> | Subject | Re: [PATCH] HZ==100 assumptions |
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Steve Underwood writes: >"Albert D. Cahalan" wrote: >> Eric Lammerts writes: >>> On Wed, 28 Jul 1999, Riley Williams wrote: >> >>>> However, the standard used by MSDOS (which I assume is what you're >>>> referring to) is for the clock to tick ~18.2 times per second (to >>>> be more accurate, 65536 ticks per hour), in which case the correct >>> >>> This is incorrect. The BIOS/MSDOS clock is generated from a 14.31818MHz >>> crystal clock divided by 12 * 65536. >> >> Nope. Clock frequency varies. Originally it was related to a standard >> video frequency. More recent computers use a frequency designed to make >> DOS timekeeping be more accurate. (the 65536 ticks/hour I suppose) > > Nope. Many modern computers use an el. cheapo clock that is just plain > inaccurate, and they don't keep time very well. Any Compaq ProLiant produced
I didn't say anything about the _quality_ of the clock. Quality is unrelated to the intended frequency.
When running without an external reference, how should Linux keep time? The kernel can assume that a video reference is used, or it can assume that the system was designed for DOS timekeeping. The kernel can't do anything about an unstable or out-of-spec clock, but it can at least start with an estimate that is appropriate for common modern hardware.
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