Xref: utzoo comp.sys.m68k:1767 comp.arch:17233 Path: utzoo!utgpu!news-server.csri.toronto.edu!clyde.concordia.ca!uunet!tut.cis.ohio-state.edu!ucsd!helios.ee.lbl.gov!nosc!marlin!aburto From: aburto@marlin.NOSC.MIL (Alfred A. Aburto) Newsgroups: comp.sys.m68k,comp.arch Subject: Re: Moto's data predicts 68040 performance well below 20 MIPS Message-ID: <1450@marlin.NOSC.MIL> Date: 19 Jul 90 23:38:35 GMT References: <1990Jul13.163849.4282@msuinfo.cl.msu.edu> <6535.26a0e67f@vax1.tcd.ie> <713@obs.unige.ch> Reply-To: aburto@marlin.nosc.mil.UUCP (Alfred A. Aburto) Organization: Naval Ocean Systems Center, San Diego Lines: 66 X-Local-Date: 19 Jul 90 16:38:35 PDT In article <713@obs.unige.ch> bartho@obs.unige.ch (PAUL BARTHOLDI, OBSERVATOIRE DE GENEVE) writes: >In article <6535.26a0e67f@vax1.tcd.ie>, rwallace@vax1.tcd.ie writes: >> In article <1990Jul13.163849.4282@msuinfo.cl.msu.edu>, fox@VIXEN.NSCL.MSU.EDU writes: >>> >>> For much of the stuff we run, 16Mhz 68020 + 68881 runs at about .8 VAX >>> mips. (Scientific technical applications). So it seems to me that >>> 25Mhz could be no faster than 25/16 * .8 = 1.25 VAX mips. >> >> Sounds like either we don't agree on what VAX MIPS mean or there's something >> seriously wrong with your system or benchmarks. The 68000 at 8MHz is rated at >> about .8 MIPS. The 68020 at 16MHz should run about 3-4 MIPS (factor of 2 for >> the clock rate, factor of 2-3 for the better design). OK, processors run below >> rated performance with depressing frequency for reasons like not enough cache >> memory, badly written code etc. but by a factor of 4??? Are you sure you >> weren't running a benchmark that proves your compiler produces code that only >> runs 25% as fast as it should? >> >> Russell Wallace, Trinity College, Dublin >> rwallace@vax1.tcd.ie >> "To summarize the summary of the summary: people are a problem" > >We have a vax 780 with FPA (== 1 MIPS) and sun 3/60 at 16 MHz with 68881, that >is the same configuration as above. All my comparisions show the sun to be >between .5 and .8 of the vax for pure computational tasks (no io). One >exception, TeX runs about twice as fast on the sun ... why ? In all cases, >I used optimization, with the fortran compiler and standard libraries (TeX >is written in pascal or C), on real problems we have run on many other machines >too. So Russells data are correct for me. Who has a 68020/68881 that runs >3-4 times faster than a 780 ? > > Paul Bartholdi, Geneva Observatory ----------- I noticed in IBM advertisements that 1 MIPS relative to the VAX-11/780 was based upon the VAX-11/780 doing 1757 (?) Dhrystones/sec. This was Version 1.1 of the Dhrystone. I don't know what particular compiler or what degree of optimizations were used (ahem, just minor points of course :-)). One VAX-11/780 may be different from another too ... In any event IF we ASSUME the 1757 Dhrys/sec is accurate for a 1 MIPS VAX-11/780 reference then we can go on and derive other possibly equally meaningless numbers (based upon other compilers with various sorts of optimizations applied). Well, I know from personal measurements that the Amiga with 25 MHz 68030 and fast nibble mode dram (with burst mode on) can do about 8200 Dhrys/sec (this is Dhrystone V2.1 which is said to be less optimizable than version V1.1 :-), but otherwise it is the same benchmark). These results indicate that the 68030 at 25 MHz is a 8200/1757 = 4.6 MIPS machine. ------------ Actually 5 MIPS for the 25 MHz 68030 is not all that unreasonable. Afterall most 68030 instructions execute in 3 Clock Cycles (implies 8.3 MIPS peak operation). Also if one operates in "synchronous" mode then many instructions execute in 2 CC's (implies 12.5 MIPS peak performance). However if we could assume (there I go again) typically 5 CC's per 68030 instruction then this implies a 5 MIPS machine. This seems very reasonable to me, but I have no hard data to examine ..... Al Aburto aburto@marlin.nosc.mil