unexpected result

[Kenneth Brody]

Yes. The most common example is early PCs that used a combination of
hardware and software to generate their video output signals. Incorrect
code and/or data could result in wildly out-of-spec video signals that
would damage (possibly spectacularly) the monitors of the time, which
were not protected against such abuse.

[...]

The Tandy TRS-80 Model II had its 2K video memory bank-switched with the
top 2K of "regular" memory. While switched in, the video signal was
turned off. Normally, this was something on the order of milliseconds,
and then the bank was switched out, and the video signal was turned back
on.

However, when TRS-DOS version 2 came out, it had despooler software as
a background task. It was placed at the top of memory, in the bank that
would be switched out when accessing video memory. It was also run at
the clock interrupt.

Well, if you didn't disable interrupts while accessing video memory, the
interrupt may come along with video memory switched in, and the interrupt
handler would then jump to the address where the despooler was supposed
to be, thereby locking up the computer, with the video signal off.

The design of the hardware was such that if you left the video signal
off too long, you could actually fry the hardware. (I believe it was a
flyback transformer that would burn out.)

Ask me how I know this.

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:[email protected]>

 

[Kenneth Brody]

[...]
On computers with old-style ferrite core memory, a tight loop that
repeatedly accessed one word of memory could cause the cores to
overheat. In extreme cases, it could literally cause a core meltdown.

I suppose if the wires bent before melting, you could have a "warp
core breach"?

[...]

And, of course, some embedded systems are *intended* to cause damage;
when the software detects that a timer or altimeter has reached a
specified value, the CPU gets blown up along with the bomb.

I suppose a software error there could cause damage to other hardware
as well.

--
+-------------------------+--------------------+-----------------------------+
| Kenneth J. Brody | www.hvcomputer.com | |
| kenbrody/at\spamcop.net | www.fptech.com | #include <std_disclaimer.h> |
+-------------------------+--------------------+-----------------------------+
Don't e-mail me at: <mailto:[email protected]>

 

[Mark McIntyre]

Keith Thompson wrote:

I suppose if the wires bent before melting, you could have a "warp
core breach"?

only when using punched cards from an old loom.

(sorry, theres a bit of a yarn to that one)

*groan*

Mark McIntyre