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From: cik@l.cc.purdue.edu (Herman Rubin)
Newsgroups: comp.arch
Subject: Re: RISC v. CISC --more misconceptions
Summary: Many other instructions are left out..
Message-ID: <998@l.cc.purdue.edu>
Date: 31 Oct 88 12:05:11 GMT
Article-I.D.: l.998
References: <156@gloom.UUCP> <18931@apple.Apple.COM> <40@sopwith.UUCP>
Organization: Purdue University Statistics Department
Lines: 29

In article <40@sopwith.UUCP>, snoopy@sopwith.UUCP (Snoopy T. Beagle) writes:
> In article <18931@apple.Apple.COM> baum@apple.UUCP (Allen Baum) writes:
> | You may find, howver, that it won't make any difference in your
> | performance because no one needs an integer multiplier very
> | often. Like a lot of things that RISC designers have left out.
> 
> I humbly disagree.  Just because *you* never use an integer multiply
> does not imply that noone else ever does.
>
There are many other operations which are cheap in hardware and expensive in
software.  Maybe we should have a "competition" to see how many operations
we can come up with for which silicon can do a quick, efficient, accurate job,
but which are clumsy and expensive in software.

I will toss in a few for starters.

	Find the distance to the next one in a bit stream FAST.  It would
be good to have an exception handler if one is not found.  I am considering
algorithms not worth implementing if the operation is slow.

	Divide an integer by an integer, obtaining a quotient and a remainder,
the choice of remainder depending on the signs of the dividend and the divisor.

	Divide a floating point number by a floating point number, obtaining
an integer quotient and a floating point remainder.  It would be nice to have
the choice of remainder depending on the signs here also.
-- 
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907
Phone: (317)494-6054
hrubin@l.cc.purdue.edu (Internet, bitnet, UUCP)