Path: utzoo!attcan!uunet!aplcen!samsung!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!iclswe!gmb From: gmb@iclswe.icl.se (Grahame Budd) Newsgroups: comp.arch Subject: Re: Electro-optic bus Message-ID: <1990Jul18.114305.3828@iclswe.icl.se> Date: 18 Jul 90 11:43:05 GMT References: Distribution: comp Organization: ICL Data AB 194 85 Upplands Vasby Sweden Lines: 24 aglew@oberon.crhc.uiuc.edu (Andy Glew) writes: >Here's a throwaway - the electro-optic star bus: Speaking of optical star busses... The International Computers Ltd, (ICL) Series39 mainframe has been using optical interconnections for six years. The bus is configured as a "local area network" where the local area is the central units of the CPU, e.g. Order Code Processors /main memory and all i/o controllers. The system is called MACROLAN. Despite the protocol overheads, (it really does run as a LAN), the transfer rate is 200Mbit/sec. Unit on the lan can be up to one kilometer apart or up to 20 km with special adaptors. This allows a CPU to be split between locations. A typical small mainframe using this system has exactly two leads between it and the outside world, the MACROLAN for highspeed i/o and an Ethernet for low speed. Larger systems tend to have multiple lans, of both sorts. The number of wires is still much reduced compared to copper connections. The latest machines to use this system are the most powerfull single, (i.e. non- vector or array), mainframe processors available, so I guess it doesn't slow the system down too much.