how fast were drum memories?

Jack Harper harper at
Thu May 10 10:15:19 CDT 2018

The Univac FASTRAND *was* slow.

You could stand there watching through the window on the side of the 
5,000-pound beast and actually see the enormous drum rotating as it 
lumbered along at, what, 14 RPS I think.

Regards to the List -


At 08:57 AM 5/10/2018, Chuck Guzis via cctalk wrote:
>On 05/10/2018 07:29 AM, Paul Koning via cctalk wrote:
> > I'm wondering what the reality of fast drum memories looked like, 
> and whether anyone came even close to these numbers.  Also, am I 
> right in thinking they are at least in principle achievable?  I 
> know I could run the stress numbers, but haven't done so.
>All of the STAR-100 stations, including the paging station used drums.
>Jim Thornton and folks at CDC ADL were working on a 100K RPM drum
>spinning in vacuo for a paging store, but they couldn't get it to work
>reliably.   At any rate, STAR was the last system I saw fast drums on
>and you can check the figures in the Bitsavers documentation under
>cdc/cyber/cyber200.  At any rate, a head-per-track drum could be much
>faster than a disk.
>There were big slow drums, also.  Consider the Univac FASTRAND unit.

Jack Harper, President
Secure Outcomes Inc
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