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From: 6600sirt@ucsbuxa.ucsb.edu (Mike O'Brien)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Whis is fastest 386/33 or 486/25 ?
Message-ID: <5943@hub.ucsb.edu>
Date: 12 Jul 90 19:50:02 GMT
References: <217@news.nd.edu>
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From article <217@news.nd.edu>, by laughner@news.nd.edu (Tom laughner):
> There would be no difference in speed between a 386 with a math
> coprocessor and a 486.  The 486 chip is a 386 + the math coprocessor in
> one.  Intel considers the 486 as a part of the 386 family.

You're assuming that just because the 486 appears as a 386+387+cache to
software, that it really is a 386+387+cache.  In reality, 85% of the
surface area of the 486 was dedicated to a RISC processor, meaning
that most 486 instructions complete in 1 clock cycle.  In addition,
the 486 can simultaneously process 5 instructions at once, as long
as those instructions don't modify the same registers or memory.
(So programmers, start writing programs that do dissimilar things
next to each other.)  Finally, the 486 can preprocess something like
2048 instructions ahead.  (Programmers: write programs that rarely
if ever jump more than 2k at a time.)

All in all, the 486 ends up being about twice as fast running
off-the-shelf software as the 386.  But if you write your program
with the ^^above^^ programming tips in mind, you can really make it
scream.

Mike O'Brien
6600sirt@ucsbuxa.ucsb.edu
no connection to Intel