Path: utzoo!attcan!uunet!samsung!zaphod.mps.ohio-state.edu!wuarchive!udel!nigel.ee.udel.edu!mccalpin From: mccalpin@perelandra.cms.udel.edu (John D. McCalpin) Newsgroups: comp.unix.aix Subject: Re: Rumour about IBM benchmarks Message-ID: Date: 14 Sep 90 01:48:42 GMT References: <1233@torsqnt.UUCP> Sender: usenet@ee.udel.edu Organization: College of Marine Studies, U. Del. Lines: 36 Nntp-Posting-Host: perelandra.cms.udel.edu In-reply-to: david@torsqnt.UUCP's message of 13 Sep 90 21:18:01 GMT >>>>> On 13 Sep 90 21:18:01 GMT, david@torsqnt.UUCP (David Haynes) said: David> I have heard a rumour that the benchmark results that IBM posted for David> their RS6000 system were the results of hand-coded, hand-optimized David> assembler coding rather than the result of compiling C or FORTRAN David> code. Can anyone confirm or deny this? I can verify that the results of the LINPACK 100x100 test case are quite valid. I have not re-run the 100x100 case specifically, but I have run numerous cases with larger matrices, and have never gotten a speed as slow as the IBM's rating! With one LINPACK-ish code (a block-mode dense linear algebra solver) I get over 13 MFLOPS for 64-bit arithmetic on a model 320! With the plain vanilla LINPACK source, I get about 8.4 MFLOPS for the 1000x1000 LINPACK test case. The MIPS rating of the RS6000's is of course entirely bogus, as it is based on the Dhrystone 1.0 (or 1.1?) benchmark. This benchmark is very easy to optimize for, both in hardware and software, and in my experience has essentially no correlation with real performance on non-floating-point work. For example, both the Motorola 88000 and IBM RS6000 score substantially higher than the MIPS R-3000 on the Dhrystone 1.1 benchmark, but the three machines have very similar scores on the 4 integer SPEC benchmarks. (I do not consider differences of +/- 25% or less as significant). On the SPEC benchmarks, the IBM RS6000 model 320 has a floating-point mean performance of about 24 times a VAX 11/780, and an integer performance of about 14 times the VAX 11/780. This level of floating-point performance is incredible, while the integer performance is not significantly different than is available in machines like the DECstation 3100 and DECstation 5000 or in the SUN Sparcstations. -- John D. McCalpin mccalpin@perelandra.cms.udel.edu Assistant Professor mccalpin@vax1.udel.edu College of Marine Studies, U. Del. J.MCCALPIN/OMNET