Messages in this thread | | | Date | Tue, 2 Nov 1999 11:47:54 +0100 | From | Harald Koenig <> | Subject | Re: Wrong bogomips after plugging in AC powery |
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On Nov 02, Orin Eman wrote:
> > timer - it has 16bit counter, and runs 18 times a second > > when 65535 is used as divider. That gives me 0.84usec precission (good > > enough). I just wonder how long it takes to do_read_hwtimer()... > > It's just a few instructions at assembly level. Windows > virtual device drivers (oh the horror) have access to a > function which returns a 64 bit count of roughly 0.8 usec > intervals since boot. It's nothing more than current timer > contents + (divider * overflows since boot). Implementing > a delay wouldn't require anywhere near as much, you just need > to be a little careful if the current value plus delay wraps.
reading that old ISA timer is awfully slow: at least 3 in/out instructions, usually 5-6 due to in_p/out_p which is 4-7.6 usec or 1600-3100 cycles on my PC!.
Harald -- All SCSI disks will from now on ___ _____ be required to send an email notice 0--,| /OOOOOOO\ 24 hours prior to complete hardware failure! <_/ / /OOOOOOOOOOO\ \ \/OOOOOOOOOOOOOOO\ \ OOOOOOOOOOOOOOOOO|// Harald Koenig, \/\/\/\/\/\/\/\/\/ Inst.f.Theoret.Astrophysik // / \\ \ koenig@tat.physik.uni-tuebingen.de ^^^^^ ^^^^^
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