Path: utzoo!mnetor!uunet!husc6!bbn!rochester!cornell!batcomputer!braner From: braner@batcomputer.tn.cornell.edu (braner) Newsgroups: comp.sys.atari.st Subject: Re: transputer Message-ID: <4679@batcomputer.tn.cornell.edu> Date: 4 May 88 13:52:40 GMT References: <28201@yale-celray.yale.UUCP> Reply-To: braner@tcgould.tn.cornell.edu (braner) Organization: Cornell Theory Center, Cornell University, Ithaca NY Lines: 41 Keywords: process communication parallel Yeah! Summary: 4 transputers == workable multitasking system [] The transputer is built to support, right in the _microcode_, multiple processes per CPU, and interprocess communication both inside the same CPU and between neighboring CPUs. The _hardware_ takes care of time-slicing between low-priority (user) processes, synchronizing communicating processes, preempting low-priority processes for high-priority wake-ups (e.g. a message sent to a system process), etc. And all with _very_ low overhead. I agree that limiting the number of concurrent processes to the number of CPUs (currently low, say 4 for a starter machine --- wish I had such a starter now...) is not a viable solution. And I agree that an MMU would be nice. BUT: many people multitask on one lousy 68000 (e.g., Amiga (shish!) or even the ST w/RTX). The main problem, as I see it, is that if one process, say the program you are developing, bombs, the whole system goes down. That's where 4 transputers w/1Meg each are good enough: 1 for you DA's, one for your compiler system, 1 for your background uploads, and still one left for your crash-prone experimental program. If the latter crashes, you reboot just that one transputer. Helios is NOT Unix. Unix is NOT designed for a multiprocessor personal machine, either. To quote a Helios document (by N.H. Garnett, Perihelion Software): "That the transputer is in need of an operating system is self evident... Most existing microprocessor OS's cannot support multi-processor hardware, even where they support multi-tasking. Unix is too large, its model of processes does not correspond to that of the transputer, and it remains essentially a uni- processor OS..." Helios is supposed to be a general OS for a network of transputers, not just for the ABAQ. Whether they did a good job of it, and whether it will take off, I have no idea. I wish somebody else was marketing it rather than uncle Jack... - Moshe Braner PS: still looking for a used 520ST system.