Path: utzoo!attcan!uunet!mcvax!diku!dkuug!dde!tpo From: tpo@dde.uucp (Thomas P.S. Olesen) Newsgroups: comp.arch Subject: Re: Is Shared Memory Necessary? Message-ID: <448@Aragorn.dde.uucp> Date: 30 May 88 21:47:57 GMT References: <685@thalia.rice.edu> <43700039@uicsrd.csrd.uiuc.edu> Reply-To: tpo@dde.uucp (Thomas Peter Sonne Olesen) Organization: Dansk Data Elektronik A/S, Herlev, Denmark Lines: 35 In article <43700039@uicsrd.csrd.uiuc.edu> turner@uicsrd.csrd.uiuc.edu writes: > >Why is it that everyone seems to assume that machines must either have >shared memory OR distributed memory, never a little of both? From my >point of view I would like to see a machine with: fast local memory; >slower, but deeply pipelined, shared memory; and a thin global sync >bus (for barrier sync). We have had memory heirarchies for decades >now, why should they cease to be useful now? The Supermax computer made by "my" company, has both distributed and shared memory. The Supermax is a multiprocessor machine with up to 8 x 68020 application processors, and up to 8 other 680x0/8085 processores for handling IO. Every processor has local memory (up to 256Mb), but they are made so they can setup the mmu and make data read/write/read-modify-write in all other cpues memory, using the common bus. But NOT instruction fetch. This achitecture makes it possible to run all processors at high speed and have fast memory access AND have shared memory. The OS is SVR3.1 and shard memory for users processes is fully supported. A memory access to another cpu is a little slower than a local access. I think remote access take about 4 times a local access. Thomas P. Olesen -- ***************************************************************************** Thomas P.S. Olesen Dansk Data Elektronik A/S E-mail: ..!mcvax!diku!dde!tpo System Software Department or tpo@dde.dk