Re: old programmer in a brand new world ...

In article <mehaase-8A91DC.23171714112005@xxxxxxxxxxxxxxxxxxxxxxxx>,
Mark Haase <mehaase@xxxxxxxxx> wrote:

> In article <43795436$0$75809$742ec2ed@xxxxxxxxxxxxxx>,
> Don Bruder <dakidd@xxxxxxxxx> wrote:
>
> > Or his own code... Nothing like blowing your pointer arithmetic and
> > pointing something like an input buffer into the guts of the program. Or
> > worse, the heart of the OS. It might not fully "explode" right away, but
> > once the PC is pointing at the data that overwrote the code that should
> > have been there, Hooo boy... Things tend to "get real western" in a big
> > hurry.
> >
> > DAMHIKT! :)
>
> I imagine that most bytes wouldn't be valid opcodes, in which case the
> processor would halt or throw some kind of error interrupt, right? Or
> did it just keep executing through the gibberish?

That depends *ENTIRELY* on the processor type (and sometimes on the
individual processor chip) involved...

An "unenhanced" Apple IIe with a 6502 processor is a prime example, even
though it isn't a mainframe like the thread originally started with -
Some 6502s would hit certain "enhanced" (65C02) instructions, and
depending on whether it was a western digital chip or somebody else's,
might execute a useful (but only to be counted on when running on *THAT
SPECIFIC CHIP*) function that you had to figure out the details of for
yourself if you were crazy enough to try to actually *USE* it, while the
next one would hit the same instruction and send the machine into a hard
lockup, another would spew a string of random bits all through memory,
and yet another one would treat that instruction exactly the same as a
NOP, leaving you without any idea that it had ever encountered a "bad"
instruction.

--
Don Bruder - dakidd@xxxxxxxxx - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info
.

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