Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!ukma!husc6!rice!sun-spots-request From: hedrick@geneva.rutgers.edu (Charles Hedrick) Newsgroups: comp.sys.sun Subject: Re: RISC MIPS -- Sun vs. VA Keywords: Miscellaneous Message-ID: <1688@brazos.Rice.edu> Date: 25 Sep 89 20:42:57 GMT Sender: root@rice.edu Organization: Sun-Spots Lines: 34 Approved: Sun-Spots@rice.edu X-Sun-Spots-Digest: Volume 8, Issue 135, message 6 of 14 In the Unix marketplace, MIPS normally means performance that many times that of a VAX 11/780, which is essentially the same as a MicroVAX 1. This led to talk of gold-plating a 780 and giving it to the NBS as the Offical MIP. MIPS are normally evaluated by trying a set of benchmarks on both a VAX and the machine involved. (I suspect that these days they probably do the VAX tests on a newer VAX and then divide by DEC's MVUP rating. MVUP is performance related to the MicroVAX 1.) Thus MIPS is not an actual count of instructions per second. Of course this only gives you a ballpark idea about a machine, since the ratio will be different for different tasks. In general it seems like RISC machines tend to perform somewhat better on simple tests than in reality. MIPS will also be different for different operating systems, so a VAX 8800 running VMS may be faster than a Sun that has the same number of "MIPS". Sun's official rating for the Sun 4/280 was 10 MIPS. That was based on some early tests, but no real user experience. I think many people now believe that for real tasks a more typical number is 8 MIPS, with 6 MIPS for Fortran (both integer and floating point). Presumably Sun is keeping its definition of MIPS constant, so you might want to multiply figures for their newer systems by the same .8 fudge factor. As far as I can tell "RISC MIPS" is used mostly by IBM for the RT. It seems to be an actual instructions per sec count. Since RISC instructions do less than the VAX instructions, "RISC MIPS" are worth less than the MIPS you normally hear quoted. The ratio is probably between 1.5 and 2.0. Nobody is very enthusiastic about MIPS, since nobody really believes you can characterize a machine by one number. Furthermore, MIPS are usually evaluated by vendors, and no two vendors use the same tests. Digital Review does a lot of testing of machines in the Unix marketplace and seems to use a consistent methodology. However their tests are almost entirely in Fortran. Because VMS has a particularly good Fortran compiler, this tends to understate the MIPS of non-DEC machines.