[FFmpeg-devel] Fwd: Fixpoint FFT optimization, with MDCT and IMDCT wrappers for audio optimization

Mike Giacomelli giac2000
Mon Aug 27 01:11:30 CEST 2007

> As opposed to recent x86 chips, where 32x32 mul is 9 times slower than add?

Modern x86 chips have pipelined adders and multipliers, so the add and
multiply rate is the same (at least assuming they have equal numbers
of each).  I believe Intel has been doing this since the pentium pro
in the mid 90s, and AMD since the K7 in the late 90s.

>Moreover, at least ARM9E and ARM11 cores execute 32x32->64 MAC in 3 cycles

Which is still 3x slower verses adds then a desktop PC made in the
last 10-15 years, hence my point about not generalizing from x86 too

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