remember, core memory is destructive read out. to read the bits you erase them and have to rewrite them.
I doubt the B * running for 30 seconds, then cancel the job would be bad, but if you started it up Friday and it ran all weekend? every time you demagnetize and re-magnetize those cores, probably an atom or two gets displaced. <pre>--Carey</pre> > On 10/31/2024 7:02 PM CDT Jon Elson via cctalk <cctalk@classiccmp.org> wrote: > > > 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
