how fast were drum memories?

[Peter Corlett]

On Thu, May 10, 2018 at 10:29:06AM -0400, Paul Koning via cctalk wrote:
> [...] So far so good. He goes on to suggest that such a drum might spin at
> 1000 revolutions per second, i.e., 60,000 rpm. That seems amazingly high. I
> could see it being physically possible for a drum of only 40 mm radius, but
> it sure doesn't sound easy.

Looking at modern hard disks, I'm unconvinced we could even mass-produce
something like that today.

A 40mm radius is comparable to a 3.5" disk, which are generally 5,400-7,200
RPM. 15,000 RPM is the fastest available, but those tend to be low-capacity and
expensive, and are often 2.5" drives with a huge heatsink. We could perhaps
rotate a very narrow smaller cylinder faster still but then the capacity
suffers further, and the seek time would start to dominate.