Very helpful! Thank you On Tue, Nov 30, 2021, 19:06 Noel Chiappa <j...@mercury.lcs.mit.edu> wrote:
> > From: Ed Cross > > > I'm currently restoring a PDP-11/70 system and need the following > > boards to complete the CPU: FP11-C > > From your mention of the FP11-C, I gather your -11/70 has a KB11-C (later) > CPU, not the KB11-B CPU of the earlier PDP-11/70's (prior to 1976 - the > difference between the two was whether they took the optional FP11-B or > FP11-C > FPP). > > Not that it makes a big difference in your case; the 4 cache cards are the > same in both. > > There used to be a seller on eBait (on the mid-East Coast - Baltimore, > IIRC) > who was selling -11/70 CPU cards (I bought a whole spare set from him) but > alas he seems to have gone away (or sold them all; a quick search, both on > eBait, and in my email, didn't turm him up; I can institute a deeper search > if need be). > > From the blog of someone who got a KB11-A working, you'll really need KM11 > cards; dunno if Guy Steele still has those clones he was selling. > > > There are definitely some versions of Unix which will run fine on -11/70's > without the FP11 (e.g. V6). The system binary is different for the > with/without versions, though: in the assembler code which saves the state > of > one process before switching to another, there is code like: > > stfps (r1)+ > > which will probably get an illegal instruction trap in kernel mode on a > machine with no FP11, and is therefore conditionally assembled (depending > on > if the particular machine the system is being built for has an FP11). > Perhaps > the later BSD versions look for the FP11 on startup, and adjust their > behaviour appropriately, but I'm not familiar with them. > > V6 as distributed contains system binary for an -11/40, which will run on > _any_ -11 UNIX will run on, and can be used to build appropriate system > binary. > > > (Diversion: I've never found out whether the KB11-B and KB11-C of the > -11/70 > used/could use the same backplane or not. By examining the prints for the > boards of the FP11-B and FP11-C, and seeing on which pins they exchanged > signals, and what signals they exchanged with the rest of the CPU, and on > which pins, it should be possible to work it out. Ditto for the M8133 ROM > and > ROM Control of the KB11-B, replaced with the M8123 in the KB11-C.) > > (Interesting factoid: the M8123 is the only card shared between any variant > of the -11/45 and -11/70: both the KB11-C and KB11-D use it. Of course, I > think we're still missing a wirelist for the -11/70 backplane, of any > variant; and the ECO history. There appears to have been at least one > poorly > documented upgrade; see here: > > http://gunkies.org/wiki/MK11_memory_system#CSR_Access > > for more.) > > Noel >
