Udelay and new CPUs

[H. Peter Anvin]

Jeremy Fitzhardinge wrote:
> 
> On 21-Jan-00 H. Peter Anvin wrote:
> > There are no "x86 cycles" on Crusoe, so it counts VLIW cycles.  In
> > fact, on TM5400 it counts *nominal* cycles, since the actual cycle
> > length is variable (due to LongRun).
> 
> So RDTSC is useless for getting consistent udelay delays.
> 

No, on the contrary.  For a 700 MHz TM5400 the TSC will always count at
700 MHz even if the CPU decides that it currently only needs to run at,
say, 175 MHz.

	-hpa

-- 
<hpa en transmeta.com> at work, <hpa en zytor.com> in private!
"Unix gives you enough rope to shoot yourself in the foot."

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