> On May 10, 2018, at 10:57 AM, Chuck Guzis via cctalk <cctalk@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.
paul
