Messages in this thread | | | Date | Fri, 21 May 1999 17:19:34 -0400 | From | Hugo Varotto <> | Subject | APIC timers in SMP [ QUESTION ] |
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Dear kernel developers,
Could somebody please route me to a place that explains how to program the timers of the local APICS ? I found the routine "setup_APIC_timer" in the file arch/i396/kernel/smp.c and I'm not absolutely sure if I understand their behaviour ( in particular, there's a comment before the definition of the RDTSC macro that says:
* The APIC timer is not exactly sync with the external timer chip, it * closely follows bus clocks.
I'd like to be able to change the timer resolution ( sometimes to 10 ms, sometimes less ), but I still don't get the relation between timer ticks and the PCI bus clocks. In the routine calibrate_APIC_clock() in the same file it seems that the kernel is reading some info from the APIC ( in bus clocks ) and some other info using RDTSC, and doing a comparison/relation between them. I'd like to understand it.
If some kind soul could give me some advice, I'll appreciate it ( I don;t want to bother, so if there's a website with the desired information, that will be great ). I'm working with an Intel SMP machine ( dual Pentium Pro ) and kernel 2.2.1 ( yes, I know it's an old version, but i think that this stuff hasn't changed a lot lately ).
If I'm saying something completely stupid regarding the timers, feel free to correct me.
Thanks in advance
Hugo
-- Hugo Varotto Computer Science Dept. University of Pittsburgh hvarotto@cs.pitt.edu
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