There are two places I'd check. The manual for the Royal McBee LGP-30 and the book Computer Structures: Readings and Examples by G Bell et al. Bill
On Thu, May 10, 2018 at 10:37 AM, Grif via cctalk <[email protected]> wrote: > > I wonder how the late generation paging disks (fixed head per track) like > DG used in the 80's compared? > > -----Original Message----- > >From: Paul Koning via cctalk <[email protected]> > >Sent: May 10, 2018 7:29 AM > >To: "General Discussion: On-Topic and Off-Topic Posts" < > [email protected]> > >Subject: how fast were drum memories? > > > >Drums were used as main memory in a number of early computers, and as > secondary memory for a while longer. I wonder how fast real ones (actually > constructed) managed to be. > > > >What prompted this question is reading an interesting document: > https://ir.cwi.nl/pub/9603 (in Dutch), "Principles of electronic > calculating machines, course notes February 1948" by Prof. A. van > Wijngaarden at the Mathematical Center (now CWI) in Amsterdam. It's quite > a fascinating short introduction into computing technology of that era. > (One comment in the intro: "The field is new. At the moment, the Eniac is > the only working machine..." -- probably not quite accurate given some > classified machines, but not too far wrong.) > > > >The section on main memory describes a bunch of different technoly > possibilities, one of them drum memory. He writes that a drum of 8 cm > diameter (a bit over 3 inches) and "a couple of decimeters height" could > hold maybe 100k bits, with a track pitch of "a few millimeters". 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. It's a good goal to strive for given that the > logic, even in the days of vacuum tubes, can run at cycle times of just a > couple of microseconds. As one more way to speed things up he suggests > having multiple rows of read/write heads, where the addressed word would be > picked up by whichever head sees it soonest. 10 rows and 60k rpm would > give you 50 microseconds average access time which "even for a parallel > computer would be a very attractive number". (Pages 17-18) > > > >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. > > > > paul > > >
