On Fri, Oct 23, 2020 at 11:57 AM Eric Smith <space...@gmail.com> wrote:
> On Wed, Oct 21, 2020 at 6:22 AM Pontus Pihlgren via cctalk < > cctalk@classiccmp.org> wrote: > I have seen PDP-15 core memory and it is not that format. It looks like >> > the memory modules from a PDP-8/I or -8/L >> > > The ME15 memory for the PDP-15 used that kind of memory [H215/H216], but > it normally used an 18-bit H215. I think there was another variant that > offered parity that would have used the 19-bit H216. > > There might have been PDP-15 memory earlier than the ME15, but at the time > of the PDP-15 introduction (1970), H21x core planes were used in most DEC > machines, so it would have been surprising for them to use something else. > Perhaps some PDP-15 systems were upgrades from the PDP-9, which used memory > modules similar to the PDP-8/I. > The PDP-15 print set on Bitsavers shows that the original PDP-15 memory was the MM15, which was in fact very similar to the PDP-8/I memory, and was available with or without parity. The ME15 must have been developed for later PDP-15 systems, and used the newer H215 core stack. I can't find any evidence of a parity version of that, which if it existed would have used the H216.
