Path: utzoo!attcan!uunet!snorkelwacker!paperboy!meissner From: meissner@osf.org (Michael Meissner) Newsgroups: comp.sys.dec Subject: Re: Whets.C benchmark VMS vs UNIX Message-ID: Date: 6 Sep 90 16:39:55 GMT References: <53@mq.UUCP> Sender: news@OSF.ORG Followup-To: comp.sys.dec Organization: Open Software Foundation Lines: 38 In-reply-to: moss@cs.umass.edu's message of 5 Sep 90 23:37:30 GMT In article moss@cs.umass.edu (Eliot Moss) writes: | Sometimes this tells a lot more about a *compiler* than it tells about | hardware. My guess is that the 80x86 compilers may not be as good at some | fancy optimizations, whereas the DEC C compiler is pretty good. If you want to | compare the hardware alone, code in assembly (but that does not give a fair | comparison if your programming will be in C). Another thing to do is to use | more similar compilers, e.g., the GNU C compielr, which I believe is available | for both of these machines/OSs. I also agree with the other respondent that it | is not necessarily a very informative benchmark; be very careful in this kind | of comparison! I would also not call a 3 MIP (or so) VAX "low-end"; one VAX | instruction can do a lot more than one 80x86 instruction in many cases, and | workstation I/O and memory systems are perhaps better designed than PC class | boxes (and mainframes even better than that, etc.). Two notes: 1) the MIPS assembler does backend optimizations -- if you use GCC with it, you get some of the optimizations normally done with the MIPS compiler suite; 2) If you are using GCC, I did a lot of tuning and patching, so you probably want to start with my patches or wait to 1.38. The experience of tuning and hacking the 88k and MIPS ports for GCC has showed me that there is a lot of stuff that can be done in the machine dependent layer of the compiler that affects performance drastically. Sometimes changing one byte (such as in a constraint) can mean quite a bit. This means that you still have an apples vs. oranges comparison if you compare GCC ports (though not as much of one). It depends on how much time & effort has been spent tuning things for each port. A young port of GCC will tend to be less optimal than it could be. -- Michael Meissner email: meissner@osf.org phone: 617-621-8861 Open Software Foundation, 11 Cambridge Center, Cambridge, MA, 02142 Do apple growers tell their kids money doesn't grow on bushes?