Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site linus.UUCP Path: utzoo!linus!brando From: brando@linus.UUCP (T. J. Brando) Newsgroups: net.micro.68k Subject: Strange MVME110-1 Bus Errors Message-ID: <633@linus.UUCP> Date: Wed, 30-Oct-85 12:20:18 EST Article-I.D.: linus.633 Posted: Wed Oct 30 12:20:18 1985 Date-Received: Fri, 1-Nov-85 00:22:50 EST Reply-To: brando@linus.UUCP (T. J. Brando) Distribution: net Organization: The MITRE Corporation, Bedford, MA Lines: 29 I am running four (4) Motorola MVME110-1 singleboards on a VMEbus backplane. The VME110 in slot 1 is jumpered to serve as VMEbus controller. If the rate at which each CPU requests the VMEbus is low enough, everything works fine. If I increase the request rate sufficiently, eventually the CPU in slot 4 doesn't get the VMEbus within 200 us, its local bus timeout counter hits bottom, and a bus error exception sequence is initiated. Fine. I can handle that. That's what you'd expect to happen. However... Here's a behavior I don't understand: All 4 CPUs experience bus errors. This stops all processing, and gives control to a simple monitor/debugger on each board (VMEbug 3.0). What I find is that a memory display command to display memory available over the VMEbus generates a bus error on the boards in slots 4, 3, and 2, but when I try the memory display on the board in slot 1 it succeeds, and if I go back to any of the other boards, the memory display succeeds on them also! Now if this isn't strange enough... sometimes the memory display on the board in slot 1 also generates a bus error, in which case I have to reset the backplane controller (and, therefore, the other 3 boards) before anyone can execute the memory display successfully! Does this make sense to anyone out there? I don't see how this could possibly be caused by my program. It seems to me to indicate some problem with the VMEbus arbiter on the controller board. Has anyone else had any experiences similar to these? HELP!!! Thom Brando linus!brando@MITRE-BEDFORD.{ARPA,BITNET,CSNET} 617-271-3156.NET {allegra,decvax,ihnp4,philabs,...}!linus!brando.UUCP