On Thu, 20 Apr 2000 18:29:48 +0100 (BST), Alan Cox wrote:
>> Can Linux cope with the new speedstep processors? Does it even care if
>> the CPU changes speed? Has anyone patched it to keep the processor in
>> highspeed mode?
>
> You should run the 2.2.15pre19 kernel with a Speedstep CPU. In most cases
> it won't actually matter because the delay loops arent as sensitive as you
> might think.
We did some tests with a StrongARM SA1100 CPU: the clock can be switched
between 58 and 265 MHZ without having to change the delay loop (although
we didn't use something timing critical yet).
> 2.2.15pre however uses the TSC correctly to get constant time delays on the
> speedstep processors.
Hmm, I wished the SA1100 had something like a TSC. I'm implementing clock
scaling, and my current plan is to calibrate the delay loop for each clock
speed (the clock can be switched in multiples of 14.something MHz on the
SA1100). If the system switches to another clock speed, the value of
loops_per_sec is updated for the correct clock speed.
Erik
-- LART. 250 MIPS under one Watt. Free hardware design files. http://www.lart.tudelft.nl/- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Sun Apr 23 2000 - 21:00:22 EST