On 10/31/24 09:35, Donald Whittemore via cctalk wrote:
If I remember right I was told back in the early 70s by our IBM CE that
physical damage could be done to our model 30 or 40 if we ran a program that
did an Assembler instruction, B * For those non-Assembler people that is an
instruction to branch to the location of the instruction. I think it might
have caused a heat problem in the core or CCROS or TROS.
Possible? Or is my 76 year old brain hallucinating?
Hammering a single location in core could overheat the
select wires, the individual cores or the select driver
cards. I can believe this could happen. I seriously doubt
it could harm the CCROS or TROS. The model 30 was SLOW, the
original version (first 1000 machines) had a 2.5 us memory
cycle time. But, a B instruction occupied 4 bytes. And the
model 30 memory was ONE SINGLE BYTE wide! So, it would have
to access 4 consecutive bytes over a 10 us period to read
the entire instruction. This would involve t different
select wires in one axis, but likely the same wire in the
other axis.
On the model 40, memory was 16 bits wide, so it would still
have to access 2 consecutive words.
Anyway, I was told that on a model 40 (I think) that if you
pressed and held stop, system reset, and load
simultaneously, it would pop a component on a circuit card
in the machine.
Jon
