🚀 go-pugleaf

In article <64429@linus.UUCP> bs@linus.UUCP (Robert D. Silverman) writes:
>In article <3532@epimass.EPI.COM> jbuck@epimass.EPI.COM (Joe Buck) writes:
>:It requires four multiplies, an addition, and a subtraction to do a
>:complex multiply; you can do this in four cycles on the TMS320C30 by
>:taking advantage of parallel multiplication and addition/subtraction.
> 
>This is not quite correct. Usually [on most hardware] multiplies take
>significantly longer than additions.

Ah, but this is what makes DSP's special: if the registers are loaded,
multiplies take one cycle.  And since most instructions allow you to
load/store/accumulate in the same cycle (as the multiply), dense
instruction sequences can be created (not usually by compilers :-)
where adds, subtracts and multiplies all cost the same.

At least, such is the case with the tms320c25, with which I am most
familiar.

-- 
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