Re: Recode to Play MP3?

[bieling@terra.es]

On May 25, 11:47 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
> biel...@terra.es wrote:
> > On May 25, 3:37 am, "Michael J. Mahon" <mjma...@aol.com> wrote:
>
> >>>Yep... The figures were right after all.
>
> >>Nope.
>
> > YEP :
>
> >>>>>Non-accelerated rates would be
> >>>>>((6+4+2)*4+3)/4=12.75 cycles/byte -->> 78.43 KB/s (slightly unrolled)
> >>>>>((6+4+2)*2+3)/2=13.50 cycles/byte -->> 74.07 KB/s (non-unrolled)
>
> OK--I wasn't looking at the formulas, just the time deltas we were
> talking about--a danger of focusing too much on the details.  ;-)
>
> These look OK except for the clock rate being 1.0205MHz and the result
> is actually "kB" (1000) rather than "KB" (1024).  Since we're comparing
> to a 11.025kHz sample rate, the "kB" number is actually handier, so the
> clock rate correction gets to 80.04kB/sec for the 4-unrolled loop and
> 75.59kB/sec for the 2-unrolled loop.
>

Hmm.. :-)

1020500/12.75/1024 = 78.16 KB/s -->> 4-unrolled loop
1020500/13.50/1024 = 73.82 KB/s -->> 2-unrolled loop

>
> Frankly, these rates are sufficiently high that it's clear something
> else is the problem.
>

These rates are 2x the actual ones seen in the real world.
Either the overhead for each sector takes about as much as the sector-
read code,
or the data is being moved twice...

--Jorge.