On Tue, 07 Mar 2006, Lee Revell wrote:
> If they are doing serious realtime DSP then they should get better
> results in userspace anyway, because they get to use the floating point
> unit which isn't allowed in the kernel.
It's not as though every algorithm needed float just because it said DSP
(some of those are actually fixed-point or something like that) at a time.
There are lots of algorithms to avoid exactly that, because it costs
performance big time. Whenever you can have integer and/or
reduce/approximate multiplication by shift+add, people will use it if
performance is of paramount importance. And such often is the difference
between having a real-time DRM software radio or not, to name just one
example I've seen in my vicinity.
In a color-space conversion tool (CCITT YUV to RGB) on P-II or P-III
(don't recall) emulating fixed point by using integers and then shifting
appropriately gave a speedup of well more than three.
There must surely be better and reasons than the FPU - licenses had
already been mentioned.
--
Matthias Andree
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