> On Apr 13, 2024, at 5:26 PM, Christopher Zach via cctalk
> <cctalk@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
