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From: chris@mimsy.umd.edu (Chris Torek)
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Re: Help-Bus Errors
Summary: minor trivia
Message-ID: <22598@mimsy.umd.edu>
Date: 17 Feb 90 16:09:04 GMT
References: <1810@lzga.ATT.COM> <1990Feb10.192028.16025@eddie.mit.edu>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 18

In article <1990Feb10.192028.16025@eddie.mit.edu> aryeh@eddie.mit.edu
(Aryeh M. Weiss) writes:
[lots of good stuff]
>SIGBUS errors are quite machine dependent ... [but include, e.g.,]
>reference an odd address with a word oriented instruction ... on Vaxes
>and 68000's ....

As someone else already mentioned, VAXen do not care about address
alignment except for speed (aligned operands are somewhat faster).
68000 and 68010 CPUs do; 68020 and 68030 CPUs do not; many RISC chips
do.  On the VAX, a SIGBUS (bus error) is caused by exactly one condition:
an address in the range 0x80000000..0xffffffff.  (Half of these are legal
kernel space addresses; from the kernel, the fault occurs for addresses
in 0xc0000000..0xffffffff.  Bus timeouts appear as machine checks rather
than faults.)
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@cs.umd.edu	Path:	uunet!mimsy!chris