What I was going on for the 5/8 similarities is some documents that I have found on Bitsavers referencing paper tapes that had both an old (PDP-5) and a new (PDP-8) part number and I thought it would be neat to have a basic PDP-5 simulator to help one learn the differences between the two systems. Well off to doing more research. Thanks Ray
On Sep 8, 2016 9:54 PM, "Bob Supnik" <[email protected]> wrote: > The PDP-5 is, in fact, not all that compatible, because it used memory > location 0 as the PC, pushing the interrupt locations to 1/2, instead of > 0/1. So any program requiring interrupts will not work on a -5 vs an -8. > The PDP-5 had an IO halt/restart facility, modeled on the PDP-1 and dropped > from the PDP-8, which allowed an IOT to "wait" for completion without > looping and testing a flag. It does not seem to have supported an EAE or > extended memory. > > The PDP-8 family (8, 8/S, 8/I and variants, 8/E and variants, 8/A) are > superset compatible for defined operations. It's possible to tell them > apart based on their behavior on undefined operations. The code for > identifying a PDP-8 is out there, but I don't have it at hand. I remember > that the behavior of RAL RAR and RTL RTR was one way of telling the 8, 8/S, > and 8/I apart. > > Most of the work for supporting models would be in the peripherals, > particularly the ones that are 'compatible' across the line (reader, punch, > terminals, clock). The pre-Omnibus machines used the older style IOP1, > IOP2, IOP4 pulse methodology; the Omnibus machines can decode all 8 > possible combinations. Beyond that, peripherals tended to be distinct: the > RK8 for the 8/I vs the RK8E for the Omnibus machines; the Type 552 DECtape > controller for the -5 and -8 vs the TC01/TC08 for the later machines. > > The "CMOS 8s" are a whole different kettle of fish. They were only used in > word processing/DECmate systems and had many unique features. > > /Bob > > On 9/8/2016 9:10 PM, [email protected] wrote: > >> Message: 1 >> Date: Thu, 8 Sep 2016 18:57:52 -0400 >> From: Ray Jewhurst<[email protected]> >> To: simh<[email protected]> >> Subject: [Simh] PDP-8: The possibilities? >> Message-ID: >> <CAMFEAABLe-s+qSZmm4AXyR8Pqhx3dPkiaDJb_aUXQo5hAHEt1g@mail. >> gmail.com> >> Content-Type: text/plain; charset="utf-8" >> >> After both reading and participating in some recent discussions, I got to >> thinking that maybe the array of PDP-8 models could be better represented. >> I say this because from what I have read very early PDP-8 code is not >> 100% >> compatible with later models conversely the PDP-5 is compatible with the >> early code and likewise uses a negibus like the Straight-8. I thank this >> could be a rewarding experience for some of us and since I can't work I >> would be able to help coordinate, write pseudo code and beta test. If >> anyone is interested in this let the discussion begin. >> >> Thanks >> Ray >> > > _______________________________________________ > Simh mailing list > [email protected] > http://mailman.trailing-edge.com/mailman/listinfo/simh
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