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.