[QUOTE=bruce.desertrat;206172]It's been going down a long time. (and I think that XComp ad is from '81) This is what you got in 1956

50 24" platters
$3800 / month lease (you couldn't buy a computer from IBM then )
3.75 megabytes

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Looks like a 'drum' store unit, with the heads translating up and down the outside of a spinning cast iron drum there was always the danger of one touching and initiating a catastrophic failure, we had a strict no entry to the computer room because one had failed and embedded chunks of drum in the concrete walls at Fawley power station. Hell we even still had a working video wire recorder in another station, steel wire and high speed were pretty dangerous too if it broke.

I worked for Idiot Bloody Management back in the 90's, we still had the house sized CNC machining cells in use making 18" platter 20 Mb hard drives to support the 25 and 50 year contracts still running.