Re: CPU frequency shifting "problems"

From: Alan Cox (
Date: Fri Sep 28 2001 - 18:09:04 EST

> > We do 5uS per transition 4 transitions per bit, 64bits. So thats 1.2mS
> > or using the PM timer thats 0.25 seconds
> OK ya lost me...;-)

I got my maths wrong by a slight factor of 1000, ignore me - there is a
reason I didnt do maths at university 8)

> Both Windows and FreeBSD-CURRENT use the PM timer for udelays. It is 3579545
> Hz. ~2.71 ticks per usec. Read the PM timer, add (2.71 * 5), loop on reading
> the PM timer until it reaches that, and (give or take) you have a 5us delay
> that does not depend on the TSC.

4MHz is not actually too bad at all, providing the reading overhead is
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Sun Sep 30 2001 - 21:01:06 EST