Path: utzoo!mnetor!uunet!husc6!cmcl2!rutgers!rochester!PT.CS.CMU.EDU!sei!sei.cmu.edu!pdb
From: pdb@sei.cmu.edu (Patrick Barron)
Newsgroups: comp.sys.dec
Subject: Re: pdp questions...
Message-ID: <3538@aw.sei.cmu.edu>
Date: 14 Dec 87 00:08:36 GMT
References: <16886@gatech.edu>
Sender: netnews@sei.cmu.edu
Reply-To: pdb@sei.cmu.edu (Pat Barron)
Organization: Carnegie-Mellon University, SEI, Pgh, Pa
Lines: 34

In article <16886@gatech.edu> ken@gatech.edu (Ken Seefried iii) writes:
>Other than the difference in busses....what is the difference between the 
>following CPU's......??
>
>the 11/23, 11/23+ and 11/24...

  The 11/23, 11/23+ and 11/24 use the exact same CPU (the F-11 chipset).  The
11/23 and 11/23+ are Q-bus, while the 11/24 is Unibus.  The 11/23+ has space
for bootstrap ROMs, and also has serial ports (two, I believe) that the 11/23
does not have.

>the 11/44 and 11/45...

   These are in fact quite different.  They use different CPUs, and the 11/45
has a special fast memory bus which the 11/44 does not have.  The 11/45 does
not support the Unibus Map, which the 11/44 has.  Also, the 11/45 and 11/55
are more-or-less the same machine.

>the 11/70, 11/73 and 11/84/83...

   The 11/70 is a big, nasty Unibus machine.  When I say "big and nasty",
I'm not kidding.  The thing needs 3-phase power to run the CPU.  The 11/73
is a Q-bus CPU with 11/70-like capability, based on the J-11 chipset.  It
has a couple of extra instructions (like the Test-and-Set instruction).  The
11/83 has a faster J-11, and a fast memory bus (the Private Memory Inter-
connect, or PMI).  The 11/84 is almost exactly an 11/83, except it's main
I/O bus is the Unibus rather than the Q-bus.

   A good reference for all this stuff is "Computer Archtecture:  A DEC
View of Hardware Systems Design", by Bell, Mudge, and McNamara.  It talks
about the PDP-n, where "n" is the number of any PDP DEC ever made, and also
a little bit about the VAX.

--Pat.