Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!zaphod.mps.ohio-state.edu!mips!kpc.com!ardent!mac From: mac@gold.kpc.com (Mike McNamara) Newsgroups: comp.arch Subject: Re: VISC - A way to speed up moto cisc mpu's? Message-ID: Date: 29 May 91 16:53:45 GMT References: <13445@dog.ee.lbl.gov> <1991May23.210000.8152@kithrup.COM> <2842@lee.SEAS.UCLA.EDU> <21621@brahms.udel.edu> Sender: uucp@kpc.com (UNIX-to-UNIX Copy) Reply-To: mac@ardent.com (Michael McNamara) Organization: Kubota Pacific Computer Incoporated, Santa Clara, CA Lines: 57 In-Reply-To: gdtltr@brahms.udel.edu's message of 23 May 91 04:48:58 GMT Nntp-Posting-Host: gold I've worked on two different commercially unsucessful heterogeneous processor machines. I don't think that I am the common thread of failure ;-) The first was the Cydrome Cydra 5, which had a 50/25 MFLOP ECL super computer wedded to a symetric 6 68020 cpu system running our MP'ized System V R3.2. This machine was introduced in 1987. The second was the Stardent Stiletto, which had two MIPS R3000, and four intel 860 processors. Each R3000 had a tightly coupled i860 which was connected as a vector processor, via our implementation of the canonical Mips write buffer chip. This is the same model we used to build the Ardent Titan super graphics workstations, altough we implemented the vector unit with gatearrays and floating point cores. The other two i860s were on a separate graphics board, with associated pixel processing power. One common problem with both machines is that the benchmark results did not justify the cost of the machine. This isn't a problem with the design of the machine, per se: Instead, it is just hard to write a benchmark that could effectively use all the power avialable on a heterogeneous machine: SPEC ran on Stiletto just as well as it would run on any machine with two 33MHz R3000/R3010 cpus. SPEC didn't "notice" that 3D graphics could go on concurrently with no performance loss. [Mashey: add a gSPEC to the mix: you must rotate a teapot while gcc'ing ;-] Another common problem with both machines is twice the technology risk exposure. At Cydrome, the ECL super computer was ready, and demonstrated at a trade show, one year before the general purposed 68020 system was ready. At Ardent/Stardent, the dual R3000 system was ready 10 months before all the bugs were ironed out of the i860 chips and our software. So, yes, Virginia, SHATOT (twice), and did not succeed. > Based on previous experience in this group, Somebody Has Already Thought > Of This. If it's true that SHATOT, then please share it with us. Of course that by no means indicates that it is not a viable proposition. However, there are bones littered on the side of the trail... -mac \___/^^\___/ ---|oo|--- || \/ -- +-----------+-----------------------------------------------------------------+ |mac@kpc.com| Increasing Software complexity lets us sell Mainframes as | | | personal computers. Carry on, X windows/Postscript/emacs/CASE!! | +-----------+-----------------------------------------------------------------+