Re: X15 alpha release: as fast as TUX but in user space (fwd)

[H. Peter Anvin]

"David S. Miller" wrote:
> 
> dean gaudet writes:
>  > i was kind of solving a different problem with the code page though -- the
>  > ability to use rdtsc on SMP boxes with processors of varying speeds and
>  > synchronizations.
> 
> A better way to solve that problem is the way UltraSPARC-III do and
> future ia64 systems will, by way of a "system tick" register which
> increments at a constant rate regardless of how the cpus are clocked.
> 
> The "system tick" pulse goes into the processor, so it's still a local
> cpu register being accessed.  Think of it as a system bus clock cycle
> counter.
> 
> Granted, you probably couldn't make changes to the hardware you were
> working on at the time :-)
> 

RDTSC in Crusoe processors does basically this.

        -hpa

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