Path: utzoo!attcan!uunet!aplcen!uakari.primate.wisc.edu!sdd.hp.com!hplabs!hpcc01!hpbbn!hpbbrd!hpfcmdd!hpfcso!hplisa!hplvli!boyne
From: boyne@hplvli.HP.COM (Art Boyne)
Newsgroups: comp.arch
Subject: Re: unexpected CPU behavior [was 486 bugs -- it's in there!]
Message-ID: <19200001@hplvli.HP.COM>
Date: 31 May 90 14:56:56 GMT
References: <350@necssd.NEC.COM>
Organization: Loveland Inst. Div
Lines: 18

csbrod@medusa.informatik.uni-erlangen.de (Claus Brod ) writes:

>Motorola's 68000 had a kind of quirk that caused a clr command to
                  ^^^
Try "has" - the 68000 has never been fixed, and it *still* is a
pain to clear I/O registers to 0 when using a compiler that likes
to optimize "x = 0" to a CLR instruction.

>first read the addressed location and then clear it. This led
>to numerous difficulties when clearing I/O registers. This one,
>however, has always been documented by Motorola, so it's more
>a feature than a bug.

It is documented, true, but a pain nevertheless, and still bites
people using HLL's.  After 7 years programming the 68000, and helping
others do so, believe me, I know!

Art Boyne, boyne@hplvla.hp.com