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From: rwa@auvax.UUCP (Ross Alexander)
Newsgroups: talk.bizarre,comp.misc
Subject: Re: What the world needs now [ is an exploding computer ]
Message-ID: <170@auvax.UUCP>
Date: Sun, 24-May-87 14:17:23 EDT
Article-I.D.: auvax.170
Posted: Sun May 24 14:17:23 1987
Date-Received: Sun, 24-May-87 21:48:23 EDT
References: <12067@topaz.rutgers.edu> <910@killer.UUCP>
Organization: Athabasca U., Alberta, Canada
Lines: 26
Summary: yes, there is such an instr
Xref: mnetor talk.bizarre:1871 comp.misc:581

In article <910@killer.UUCP>, jfh@killer.UUCP (John Haugh) writes:
> A friend of mine [...] told me [...] that one of the unused op-codes
> in the M6800 had the nasty side effect of overloading the bus and causing
> much grief on the PC board the chip was mounted on...
> You don't really expect me to believe that this actually happened now do
> you? Anybody out there heard of anything like this really happening?

The opcode exists, the mnemonic is HCF (Halt and Catch Fire) :-) and
without my manuals I can't recall the hex.  It's a manufacturability
instruction, for testing the chip after the wafers are cut apart, and
before they mount the dies onto carriers.  It just counts 0000 to FFFF
on the address buss continuously.

As far as this sort of thing in the mainframe world goes, I (fondly)
remember that one of the hackers at the MFCF (U of Waterloo, about
197[45]?), I believe it was C.J.  O'Donnel (corrections solicited,
any of you guys still around???)  found out that if one could
synchronously produce a tag fault, a lockup fault and some third
fault which I forget (a derail??)  that the fault priority arbitrator
would fry a diode or something and <*crash*> until the CE could fix
it.  Of course, this was done more than once - it has to be
repeatable to be a scientific experiment, right ;-) !!  So be careful
about generating faults on an H6050.  And this is _not_ hearsay - I
saw the code and experienced the crashes.

...!ihnp4!alberta!auvax!rwa	Ross Alexander, Athabasca University