[x264-devel] [PATCH] Add all remaining 16x16 predict Altivec routines

Loren Merritt lorenm at u.washington.edu
Wed Jan 14 13:41:54 CET 2009

On Tue, 13 Jan 2009, Alexander Strange wrote:
> On Jan 13, 2009, at 4:06 PM, Antoine Gerschenfeld wrote:
>> I got the following numbers from checkasm by calling the
>> mach_absolute_time() function (counts nanoseconds) on MacOSX instead
>> of rdtsc.
>> I don't know how accurate they are : it seems you can't access the PPC
>> performance counters on Darwin without a driver.
> It's accurate enough - PPC isn't severely out-of-order like x86, and the 
> units aren't CPU ticks so won't change meaning if it speedsteps.

If you count CPU cycles then benchmarks are consistent across speedstep, 
whereas if you count realtime then the functions still take the same 
number of cycles which corresponds to different times.

--Loren Merritt

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