Path: utzoo!utgpu!watserv1!watdragon!lion!ccplumb From: ccplumb@lion.waterloo.edu (Colin Plumb) Newsgroups: comp.arch Subject: Re: Bus Partitioning? Message-ID: <20835@watdragon.waterloo.edu> Date: 13 Feb 90 02:54:00 GMT References: <1990Jan30.174807.14657@ncsuvx.ncsu.edu> <2073@crdos1.crd.ge.COM> <19597@bellcore.bellcore.com> Sender: daemon@watdragon.waterloo.edu Reply-To: ccplumb@lion.waterloo.edu (Colin Plumb) Organization: U. of Waterloo, Ontario Lines: 23 In article aglew@dwarfs.csg.uiuc.edu (Andy Glew) writes: >One of the busses may be designated the "global" bus, listened to by all >processors. > Others might be allocated to connect groups of processors (and I/O >controllers) as needed. This reconfiguration would be done infrequently. > So, for example, if you have an I/O going on, allocate it a bus >for the (long) duration of the I/O. > Or, if a group of programs appear to communicate heavily, allocate >them a private bus. There exists a commercial product that looks like this: The Cogent Research (Beaverton, Oregon) XTM. A box of processors has a parallel broadcast bus, used for exchanging synchronisation information, and 4 32-way crossbar switches connecting the 20-Mbit/sec serial DMA links of the transputers. These get used for sending larger messages (like file I/O) around. The link controller is a dedicated processor that also lives on the global broadcast bus. It's a lot faster than a LAN (I forget exactly, but channel setup times are a few microseconds), but a lot slower than a processor bus. So somebody thinks it's a good idea... :-) -- -Colin