Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mandrill!gatech!hubcap!mrspock From: mrspock@hubcap.UUCP (Steve Benz) Newsgroups: comp.unix.microport Subject: Re: SOP Benchmark: 286 Unix vs. 386 Unix Message-ID: <2031@hubcap.UUCP> Date: 25 Jun 88 16:53:46 GMT References: <2173@sugar.UUCP> Organization: Clemson University, Clemson, SC Lines: 21 From article <2173@sugar.UUCP>, by karl@sugar.UUCP (Karl Lehenbauer): > It is somewhat surprising to me that the 386 would outperform the 286 > by a greater than 10-to-1 margin. I would expect 3-to-1 from the clock > and bus width differences. I attribute the rest of the difference to > the much nicer instruction set provided by the 386 in native mode > (more registers and it's much more orthogonal) and the reduced overhead > of not having to manipulate segment registers. I'd say it has alot to do with 32-bit pointer manipulations. It takes in many cases 6 instructions just to *copy* one pointer to another -- I wouldn't even want to think about how many cycles are involved in such an operation. On the 386 it's two instructions for (I think, but I could be wrong) all cases of 32bit-32bit moves. (At least all the cases that pcc will generate.) You wouldn't do so well if you were comparing a 286 program in small model to a 386 program. > -- uunet!sugar!karl - Steve Benz