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From: denbeste@bbn.com (Steven Den Beste)
Newsgroups: comp.sys.amiga
Subject: Re: 68040 vs 80246 (Was Re: Xerox sues Apple!!!)
Message-ID: <49900@bbn.COM>
Date: 19 Dec 89 14:46:37 GMT
References: <819@mindlink.UUCP>
Sender: news@bbn.COM
Reply-To: denbeste@BBN.COM (Steven Den Beste)
Organization: Bolt Beranek and Newman Inc., Cambridge MA
Lines: 29

In article <819@mindlink.UUCP> a218@mindlink.UUCP (Charlie Gibbs) writes:
>
>     I seem to recall that the 386 was released with bugs too.  As
>for the 286, I hear that IBM went so far as to hardwire fixes that
>depended on the bug being there, and Intel *couldn't* fix it later.
>
>     I haven't heard similar stories about the 680x0 line, but of
>course that doesn't mean that there have been no problems.  On the
>other hand, maybe Motorola takes longer to get a chip out the door
>because they work harder at getting the bugs out first.

The original release of the 68000 had a bug in the "page fault" interrupt,
so that it pushed the STACK POINTER onto the stack frame instead of the RETURN
ADDRESS. Needless to say, this made it pretty hard to use an MMU with a 68000.

One of the very first machines with a 68000 and MMU (it may have been from
Apollo, my memory is hazy) actually had TWO 68000's, with one runnine one
instruction ahead of the other. When the leading 68000 got a page-fault, the
trailing one got a different, correctly working interrupt. It would then fix up
the stack frame for the leading 68000 and massage the MMU.

Is that ugly enough for you? (I might mention that in the Intel vs. Motorola
fight, I'm a firm Motorola fan. But let's keep things in perspective here, OK?)


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