Welcome to us Pa's Minicomputer Website
Theo Engel

This web site collects bits and bytes to be shared with other people. One of my interests is computer emulation of both new and old hardware systems. From the sixties, Honeywell's 16-bit minicomputers are taken as start. A 12k DDP-516 was the first computer I ever worked with and determined my working life to a large extent. Now, being retired after working 40 years in ICT, there is time to play with computers just for fun and to explore subjects for which there was no time before.

Spending time to old computers may look worthless in that context. However for young people it is hard to imagine how the ICT discipline, and how fast that discipline developed over the past 50 years. Computers of 50, 40 years ago were very different from the small boxes we have today. Not only the size was different, also their capabilities and costs have hardly any relation to what we call computers today. Also the software, the development tools, the languages were primitive compared with today's standards.

May be caused by the fast development of the computer industry over the last 50 years and the shake out of so many computer companies during those years, much of that development looms to be forgotten. Hardware and software of the past may be labeled today as primitive. It is however good to understand that many of the developments at that time were milestones on the way to get the computer systems as we have them today.

The interest in computer history is growing. Sites on the web start to collect bits and pieces of the information systems of the past in order to contain some of those exiting milestones. One milestone was the creation in the sixties of "the minicomputer": a relatively small and low cost box at that time, with a real computer in it.



This site is about the software simulation of the 16 bit Honeywell DDP516/316 (sold by Philips as P9202/P9205) and the Philips 16 bit P800 minicomputers. In addition to that, software and documentation for both can be found on this web site. Collecting (and restoration of) software and documentation for these computers is an ongoing effort and is / will be published step by step.

Also the result of rebuilding these mini's with an FPGA (Field Programmable Gate Array) is / will be published. This provides me the opportunity to learn a new technology to build hardware. And, by using it for rebuilding a machine I worked with say 40/50 years ago, it also is a nice illustration of Moore's law. In less than 50 years, cabinets with logic circuitry disappear in the corner of a small chip which only costs a few dollars. while the old, well known programs are still able to run.


Honeywell Series 16

Machines of the Honeywell Series 16 computer line, starting with the DDP-116, were the first (may be the first) minicomputers that used 16 bit words, which size became the minicomputer standard. Most of its (later disk oriented) software is lost, but due to efforts of some people active on the web, a large part of its standard paper tape software is still there. This software, together with a working hardware emulator of the DDP-516/H-316 machine, gives the possibility to get a flavor of a "state of the art" minicomputer of the mid-sixties. Part of this web site is devoted to that subject.

DDPx16 Pages

Simulation of the DDP-516/H316


Philips P800 Series

Philips Electronics marketed the Honeywell 16 bit machines (OEM, as P9200 range) until Philips came in 1971 with its own minicomputer line, the P800. Reflecting the state of the art of 1970, machines of this family had a much more sophisticated set of features and software than for instance the Honeywell machines which reflect a typical minicomputer design of the sixties. Although the P800 became a popular building block in many different types of systems, there is nothing (.. almost nothing) about these systems on the Web. Is everything about these systems really gone ??

I worked with P800's during the period 1972-1980 and only still own a few documents describing the instruction set and some programs. In November 2007, when my first version of a P855/P860 simulator was published, this text finished with the remark: "I am interested to make a P800 emulator and have some prototype working, but unfortunately software is completely lacking". This remark was followed by the question to contact me in case of sharing interest in the P800 machines or having either documentation or software available for these machines. This yielded a few interesting reactions with as result that some of the original P800 software (and documentation) popped up, which can now be made available in combination with the simulator. So happily the situation (end 2008) is much better than a year ago: with original P856 software there is now a working simulator prototype of the P856, while the P855/P860 is improved. Whether the P855/P860 simulator will work as the real one is of course still unknown, because original software for that machine is still lacking. But having the P856 working with some of its original software is a major step forward and the results will be successively published on this web site.

The question remains however:

Please contact me in case of sharing interest in the P800 history, its technology and software, or in case of having some of its software or documentation. Not everything is lost yet; but may be some other software (for the P855/P860 for instance) pops up from one of the dark corners, where we put items without value anymore. Would be nice and, who knows, may make it possible to add a few other bits to the history of computers.

Most wanted P800 items:
- A (pdf of) P800 Macro Processor Manual (MAC) (Load Module is available)
- Original P855/P860 software (to validate the P860 simulator)

  ** Any help to recover one of these items is highly appreciated; please contact: info@theoengel.nl **

P800 Pages

P855/860 Simulation

P856 Simulation (most recent P856 simulator version is 0.045 Feb 26 2017)


Rebuilding a Mini with an FPGA (Field Programmable Gate Array)

Summer 2009 I discovered a, at least for me, new technology that looked to be excellent for rebuilding a historic computer. I knew about FPGA's predecessors, like PLA's, but those could only be used with specialized tools and just for a part of the logic of a computer. Apparently also the progress in that area is big: to my surprise, FPGA technology is affordable now for hobby use at home and can be programmed with a common PC. Promising: the threshold to start using this technology is low! But where to start? No idea how big an FPGA should be to contain the logic of a mini; no idea how to program logic, which programming language to use, how to connect peripherals, etc., etc.

So although it is easy to consider to start using an FPGA for rebuilding an old mini, it quickly turned out that there is to beat a learning curve. Half a year later now (January 2010) the results of my experiences are that far, that I got the idea to add them to this web site, as an other technique and addition to the software emulation of old computers. Is this called hardware emulation ?

The first fruit of my efforts is a working rebuild of the Honeywell 316/516 and because it did not falsify my first expectations of this challenging technology, others will follow. For details, please look at the link below. Being a first exercise, improvements are certainly possible, so feedback will be appreciated.

X16 FPGA implementation


The second exercise is a FPGA implementation of one of the members of the P800 family of Philips Minicomputers: a P856. In addition to supporting a console typewriter and a papertape reader and puncher, this implementation supports two moving head disk units by using the SD-card of the FPGA development board. Loaded with original P800 software, the DOS operating system, including Assembler and Fortran, is running from the SD-card.

P856 FPGA implementation


Site History

Feb 26 2017

P800: P856 simulator version 0.045.

Feb 4 2017

P800: P856 simulator version 0.044 added.
DDP-516_2 (64bit) as: SimX16 replacement added.

Jan 14 2017

P800: P856 simulator update (version 0.043).
DDP-516_1 (32bit): SimX16 is replaced by DDP516 (SimX16 still available).

Jan 14 2012

P800: P856 simulator update (version 0.040).
FPGA-P8: page updated with details about the used/preparation of the sd-card as 2 X1215 units.

Dec 18 2011

P800: page added about the FPGA implementation of a Philips P856 minicomputer (P8-01).

Dec 15 2011

P800: P856 simulator update (version 0.039); new 2ptr.pl (running under Windows and Linux); p8asm.pl now also generates an .hex output file for P800-fpga test programs; leditf runs both on simulator and P800-fpga

Nov 7 2011

FPGA-X16: Version X16-04: When X16-03 was compiled with Quartus 10.1sp1, the Instruction Register was loaded sometimes with a wrong value, probably caused by a timing problem. In version X16-04 the timing problem is solved by adding additional states in the fetch/decode logic.

Aug 5 2011

P800: P856 simulator update (version 0.038)

Jan 24 2010

FPGA-X16: Version X16-03 added. Supports a faster papertape reader (100 cps i.s.o 20 cps).

Jan 19 2010

FPGA-X16: Demo: Fortran IV program compilation, load and execution. X16Panel version 7. X16_Cpu version 023.

Jan 18 2010

FPGA-X16: Test and demo added: X16 running MTK16.

Jan 17 2010

FPGA-X16: X16 page updated. Added Extended Mode test program TX16E-1. X16_Cpu_021.v replaces the previous X16_Cpu_02.v and X16Asm-04 uploaded again to the X16 archive directory.

Jan 15 2010

FPGA-X16: X16 upgraded with Extended addressing and 32Kword support (X16-02). Demo added showing a DAP16 assembly and LDR-APM link/load.

Jan 10 2010

FPGA-X16: Page extended and new versions of X16Panel, X16Asm and TX16

Jan 7 2010

FPGA-X16: Page added about the X16 FPGA implementation of a Honeywell 316/516 minicomputer

Sept 8 2009

P800: P856 simulator update (version 0.034).

March 2 2009

Few editorial updates on the Home page and the DDP-x16 page.

Jan 5 2009

P800: P856 simulator update (version 0.032). Few editorial updates on the P856 page.

Dec 29 2008

P800: P800 page updated and documentation added about the Disc Real Time Monitor (DRTM) internals.

Dec 16 2008

P800: Some other scanned documents added: P800 Assembly Language specification, a detailed specification of the P800 instruction set and the Disc Real Time Monitor (DRTM) manual (partly yet).

Dec 9 2008

P800: Some scanned documents added: Reference Cards , the Disc Operating Monitor (DOM) manual and the P856M/P857M System Handbook.

Dec 1 2008

H316: Page added with examples of the usage of the standard papertape software (assembler, loader, Fortran compiler, ... ). The Fortran compiler part of the software archive is updated.

Oct 14 2008

P800: P856 page added, showing some working examples of the P856 simulator with original P800 software (DOS5, X1215 formatter, Assembler, Linker, Basic, High Speed Fortran, ...).

Oct 10 2008

P800: first issue of a P856 simulator (P856-03.pl), working with and including with some original P800 software (DOS, Assembler, Linker, Basic, High Speed Fortran, ...). Updates for the P855/P860 simulator (version 0.091), and other utilities.

July 3 2008

P800: a generous person supplied a number of disk images of real P800 (X1215) disks. This not only makes some of the real P800 software available, but also lacking info so far about the disk format. I used a number of assumptions (notified in the applicable programs, e.g. in premark). With the original info available, some of these assumptions are corrected by means of updates (simulator, loader, assembler, IPL, disk image). It is still not possible to boot the simulator from the provided disk images, because the monitors on these images are configured for the P856. So in order to use these images, the simulator must be adapted to a P856, which is one of the next things to do.

April 3 2008

P800: simulator version 0.8 (some fixes). Loader version 0.7, includes linking multiple modules from the command line and the linking of object libraries. Utilities added to prepare object libraries. Assembler version 0.6 with a few additional features.

Dec 22 2007

P800: page added about the use of the simulated moving head disk (Philips X1210)

Dec 19 2007

P800: simulator version 0.7 with moving head disk support, boot/IPL from disk and the option to load a relocatable load module. Loader extended with the option to generate a relocatable load module. Utilities to premark/prepare a disk image for the moving head disk.

Nov 24 2007

P800: simulator version 0.6, adapted with a small change to also run under control of Windows with a Perl compiled for MSWin32.

Nov 21 2007

P800: simulator version 0.5, extended with card reader + update mpx channel input logic. ledit extended with card reader input support.

Nov 13 2007

P800: simulator, assembler, loader, update to version 0.4

Nov 7 2007

1st issue of the pages about the P800, a P855/P860 simulator, assembler, loader + a few demo programs

Oct 10 2007

MTK16 (Multi Tasking Kernel for DDP-516/H-316) added to software archive + an experimental moving head disk driver (both, non-Honeywell originated software !)

May 19 2007

SimX16 (GUI for DDP-516/H316) version 0.91 published (based on SIMH 3.7-0 with RTC patch) + few editorial changes

March 28 2007

SimX16 (GUI for DDP-516/H316) version 0.90 published (based on SIMH 3.7-0)

Jan 23 2007

DDP-516 console: control and operation pages added

Jan 16 2007

SimX16 (GUI for DDP-516/H316) version 0.89 published (based on SIMH 3.6-1)

Dec 15 2006

Magtape and Fortran IOS object modules added to software archive (DDP-516/H316)

Dec 6 2006

Site online and first publication of the software archive (DDP-516/H316 papertape drivers)


Page last updated on: February 26 2017 | Contact: Info@theoengel.nl