On Tue, 23 Apr 2002, Andi Kleen wrote:
> That's the local APIC timer. Pretty much all modern x86 have it.
> But at least microsoft warns from using them for high precision
> tim ekeeping on their mmtimer page "due to inaccuracy and
> frequent silicon bugs" (and I guess they have the data for that)
That's nothing new -- I recall a problem of missing half a tick each
time when hardware reloads the timer after reaching zero with certain
revisions of Pentium CPUs. It is documented in the specification update.
> The linux local APIC timer setup could be probably also improved, for
> example the 16 multiplier is a bit dubious and the calibration does not
> look very robust.
When fiddling with the predivider, please keep in mind the i82489DX only
supports 2, 4, 8 and 16 as dividers and you may set up 1 (i.e. no
division) but in a different way -- by setting LVTT appropriately (use
SET_APIC_TIMER_BASE(APIC_TIMER_BASE_CLKIN)).
-- + Maciej W. Rozycki, Technical University of Gdansk, Poland + +--------------------------------------------------------------+ + e-mail: macro@ds2.pg.gda.pl, PGP key available +- 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/
This archive was generated by hypermail 2b29 : Tue Apr 30 2002 - 22:00:09 EST