how fast were drum memories?
paulkoning at comcast.net
Thu May 10 11:22:31 CDT 2018
> On May 10, 2018, at 10:57 AM, Chuck Guzis via cctalk <cctalk at classiccmp.org> 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.
Faster than a moving head disk, certainly, though head per track disks also existed. DEC had some fast ones -- RS04 comes to mind.
I looked at the Star peripherals manual. It describes the paging drum as a modified 865 drum, which "rotates at 1800 rpm". So it might have a high transfer rate -- 12 bit words in parallel from 12 heads -- but clearly quite high latency.
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