From owner-freebsd-chat Mon Feb 10 17:18:53 1997 Return-Path: Received: (from root@localhost) by freefall.freebsd.org (8.8.5/8.8.5) id RAA00718 for chat-outgoing; Mon, 10 Feb 1997 17:18:53 -0800 (PST) Received: from who.cdrom.com (who.cdrom.com [204.216.27.3]) by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id RAA00667 for ; Mon, 10 Feb 1997 17:18:46 -0800 (PST) Received: from sax.sax.de (sax.sax.de [193.175.26.33]) by who.cdrom.com (8.7.5/8.6.11) with SMTP id QAA29304 for ; Mon, 10 Feb 1997 16:52:13 -0800 (PST) Received: (from uucp@localhost) by sax.sax.de (8.6.12/8.6.12-s1) with UUCP id BAA29856; Tue, 11 Feb 1997 01:50:30 +0100 Received: (from j@localhost) by uriah.heep.sax.de (8.8.5/8.6.9) id BAA21264; Tue, 11 Feb 1997 01:29:01 +0100 (MET) Message-ID: Date: Tue, 11 Feb 1997 01:29:00 +0100 From: j@uriah.heep.sax.de (J Wunsch) To: hans@brandinnovators.com (Hans Zuidam) Cc: freebsd-chat@FreeBSD.org, cmott@srv.net Subject: Re: Bus Errors References: <199702100848.JAA22878@truk.brandinnovators.com> X-Mailer: Mutt 0.55-PL10 Mime-Version: 1.0 X-Phone: +49-351-2012 669 X-PGP-Fingerprint: DC 47 E6 E4 FF A6 E9 8F 93 21 E0 7D F9 12 D6 4E Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) In-Reply-To: <199702100848.JAA22878@truk.brandinnovators.com>; from Hans Zuidam on Feb 10, 1997 09:48:15 +0100 Sender: owner-chat@FreeBSD.org X-Loop: FreeBSD.org Precedence: bulk (Moved to -chat, since it's getting hysterical now...) As Hans Zuidam wrote: > > > What does "Bus error" mean? > > Amazingly enough, a buss error is a memory allocation error. At least it > > was under SunOS. I am guessing FreeBSD is the same on this. > The term "Bus error" originated from the Motorola M68K ... No. Unix hasn't been developed on the m68k. :-) It's been developed on the PDP-11. But you're right, the m68k bus interfaces behave similar to the usual PDP-11 bus interfaces: accesses to bus addresses that are not `wired' will simply hang the bus. The workaround for this was a watchdog timer that caused a processor trap, just the bus error. Looking hard at the signal names, you'll see that the first of them map to the PDP-11 traps. Or does anybody still know what SIGIOT's and SIGEMT's were good for? IIRC, an EMT [emulator trap] has been used to extend the instruction set of the CPU in software, e.g. like an FPU emulator, something that's been invented back in the early days of the PDP-11, too. IOT was the IO trap, i think external devices could hardware-trigger this one when they required attention. There's more PDP-11 inheritage, see spl(9) for another example. In particular, the historic (no longer in BSD) numerical values spl0() through spl7() mapped directly to PDP-11 instructions. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)