Path: utzoo!attcan!uunet!ginosko!husc6!rice!sun-spots-request From: convex!datri@uunet.uu.net Newsgroups: comp.sys.sun Subject: Re: RISC MIPS -- Sun vs. VA Keywords: Miscellaneous Message-ID: <1724@brazos.Rice.edu> Date: 27 Sep 89 14:48:03 GMT Sender: root@rice.edu Organization: Sun-Spots Lines: 24 Approved: Sun-Spots@rice.edu X-Sun-Spots-Digest: Volume 8, Issue 139, message 3 of 11 >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 I'm pretty sure you're thinking of the MVII, which is usually rated at about .9 of a 780. As I remember, the MVI was significantly slower. >Thus MIPS is not an actual count of instructions per second. Million Instructions Per Second. The problem is, as you noted, that many people compare those figures across architectures. It may also be significant how they come up with that number -- do they just average out all the instruction times and divide by n, or do they weight it according to the instructions that people actually use? On the MVII chipset, DEC implemented some of the "lesser-used" instructions in software, which could skew the meaning of an MVII "MIP" according to what you do on it. An example is the CRC instruction, which it seems DEC did in software, but of which the VMS BACKUP program makes heavy use. I prefer the habit of saying "10 times a 780" or "10 VAX MIPS", since that's a more useful number. Another thing to be careful about is that there is a manufacturer named MIPS who make RISCish processors (and machines), and that the DECstation 3100 uses them.