On Fri, 23 Apr 1999 00:21:46 -0400 (EDT), <kernel@vdr.qc.ca> said:
> I have a simple question. What the h... is a bogomips ? I think it
> has to do with the time a cpu takes to do a certain number of software
> loops. Is that it ?
Yes.
> If so, how is the number measured ?
Search linux/init/main.c for "bogomips" to see the algorithm; it's in
the "calibrate_delay" function. It basically adjusts the guessed
loops-per-clock-tick until it gets exactly one tick per timer loop.
There are two reasons for having bogomips. The first is that it
calibrates the "__delay" busy-wait loop so that we can perform
microsecond-accurate delays in the kernel for use when talking to
certain devices. The second is so that people can brag about how studly
their CPUs are. Support for that second reason is surprisingly strong:
there is an outcry every time anyone suggests removing the public
display of bogomips during startup. :)
--Stephen
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