Re: 50 MB in the '80s?
"Notable in the early '70s, perhaps, when EDS4 and EDS8 packs were normal (detect the ICL experience) but by the mid to late '70s EDS200 was the standard size."
Back in the early to mid 80s we had 200 and 300 MB disk packs. The older guys said that the 200s replaced 50 MB and smaller packs.
"I have never seen a disc drive 'walk'."
Lucky you.I have. I also had to fi the resulting mess.
"Of course they may have been fixed down, but given the delicacy of alignment I would have thought a vibration severe enough to shift the drive cabinet would have had an impact on the platters."
You'd be perfectly correct. Oh, was there ever an impact.