15 Apr
2024
15 Apr
'24
6:25 a.m.
On Apr 13, 2024, at 5:26 PM, Christopher Zach via
cctalk <cctalk(a)classiccmp.org> wrote:
Was reading the Wikipedia article on Drum memories:
https://en.wikipedia.org/wiki/Drum_memory#External_links
And came across this tidbit.
As late as 1980, PDP-11/45 machines using magnetic core main memory and drums for
swapping were still in use at many of the original UNIX sites.
Any thoughts on what they are talking about? I could see running the RS03/RS04 on a 11/45
with the dual Unibus configured so the RS03's talk to memory directly instead of the
Unibus, but that's not quite the same as true drum memory.
Closest thing I remember was the DF32 on a pdp8 which could be addressed by word as
opposed to track/sector.
Thoughts?
C
I don't know of any drums on PDP-11 systems. RS03/04 are of course fixed head disks,
as are the earlier RF11 and RC11/RS64. All these are functional analogs of drums in that
they have no seek time. Are drums usually word addressable? That doesn't seem
necessary, not unless you use them as main memory. Even the early ARMAC (1956-ish) which
uses a drum for main memory doesn't really need it to be word-addressable because it
had a one-track buffer memory (think of it as an early cache). If you want
word-addressable, the RF11 will do that. Not the RC11, it has 32 word sectors.
paul