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PDP-11 on the S-100 bus

FWIW, I think that when this concept is looked at more carefully in light of current knowledge, the correct level to pursue integration would be based on a Qbus-to-S100 interface, not at the CPU-chip level (whether the LSI-11, F-11, or J-11).  In general, it's also less expensive to get one of the basic-CPU DEC modules than buying gold-top CPU chip(s) -- which unfortunately get chip-collector prices.
Working at the Qbus-level also gives you a clean interface specification from which to work.  If all of the necessary HW fits onto a single S-100 board, then the form-factor of a DEC dual-height module works nicely as a daughterboard there (there are dual-height DEC modules for all three of those CPUs).  Getting 16-bit memory transfers and master-slave working ought to be straightforward.  I/O gets more interesting.
(Note that for the F-11 CPU typically you'll want the accompanying Memory Management chip: http://simh.trailing-edge.com/semi/f11.html)
Working at the Qbus-level also means that you could start with a working system on the Qbus side and then work through transfering functions to the S-100-side over time.  Starting with memory, IMO, but with console I/O to closely follow I'd think.
FYI, the following is a short, relevent, read (although based on the Unibus, not Qbus): http://inspirehep.net/record/133897/files/fermilab-tm-0772.PDF
It's been pointed out in the past that one would still have to build up their own software stack to the degree that one can't use S-100-native resources to substitute for Qbus-native functions; I don't think that trying to run RT-11 with DEC-drivers is going to happen if there are S-100-specific variances.  But I'm no expert, and I'd sure like to hear otherwise ...

On Wed, Jul 30, 2014 at 2:16 PM, John Monahan <mon...@vitasoft.org> wrote:

If we are thinking PDP, there was that Alpha Micro Western Digital WD16 based board which was essentially a PDP-11 on the S-100 bus.  See:-




It was a 4 chip set but ran at 4MHz.  The two board set was popular with small business for a time. However I’m not sure it would be practical for an  OS today.  Would also be a lot of work also to draw up a board  (actually probably 2 boards though with GAL’s could probably get by with one).  


I’m thinking if we wander from the purest approach, and shoehorn a powerful CPU on to the S100 bus,  may as well get a fast one and have done with it.  I’m really impressed with how the 80386 splices into the bus with two speeds.  One for RAM, one for I/O.  Should be possible to do the same with other CPU’s





From: n8vem...@googlegroups.com [mailto:n8vem...@googlegroups.com] On Behalf Of David Fry
Sent: Wednesday, July 30, 2014 9:51 AM
To: n8vem...@googlegroups.com
Subject: [N8VEM-S100:4751] Re: An ARM CPU on the S100 bus


Hi John,


both Vince and Andrew have made mention of an interest in seeing a version of DEC mini computer technology brought onto the S100 bus (if this is possible).

This idea is beginning to grow on me and I would like to add my interest to the number (now 3 :-) )

I have no experience whatsoever in this area of vintage computing, but what a trip down the history of computing it could be.


I noticed that the HD1-6120 seems to be available in small numbers (including from UT source)


and also the DCJ11 although price is somewhat higher


or maybe some other significant vintage mini...., again I'm not sure how practical a suggestion this is but with the Z80 done and the Intel x86 track done my processor interests are now covered.




David Fry

On Tuesday, July 29, 2014 6:58:58 PM UTC+1, monahanz wrote:

I have been doing some long term planning as to the direction I would take in doing new S100 boards.  To recap, we now have a 6502, Z80, 8080 (Josh), 68000, 8088, 8086, 80286 and soon an 80386 set of boards on the S1000 bus.  Andrew and I have already started laying out an 80486 board. 


Since I do a lot of flying on business I have time to read up on chips and recently I have been thinking what would be the best way to get ARM CPU's on the bus.  There are many types, and while one could start with a bare chip it does seem to make more sense to start with an embedded module.  There are many of these, most of which boot up Linux immediately.  One particular one I'm fairly impressed with is an Italian one called "Aria G25"   see:-




Also it lends itself to easy pin splicing/layout on a board. It has good documentation and software support. I particularly like the fact that it has 60 GPIO pins.  These could be easily spliced into our S100 bus so we could use our current boards for I/O.  (In fact at 400MHz, one could also use the S100 RAM!).   I know some of you will view this as sticking a Lamborghini engine in a Volkswagen, but would it not be neat to see Linus running on the S100 bus.


Comments please, in particular I would be interested in any other similar modules.




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