MAE (Macro Assembler Text Editor) or ASSM/TED is a program sold by Eastern House Software for the KIM-1, Apple, PET, C64 and more 6502 based machines.

RAE was the name by Synertek for MAE, as ROMs for the SYM-1 which could be installed to add the Resident Assembler/Editor (RAE). Synertek contracted Eastern House Software to port their Macro Assembler/Editor (MAE) into an 8 KB ROM. AS you can see in the reconstructed source, the adaptations were not much more than adding the SYM-1 I/O such as character I/O and tape handling, the essence of MAE stayed as RAE. It was not that popular in the SYM-1 world, even Synertek used internally another assembler, with more MOS Technology compatible syntax.

The author of MAE and RAE, was Carl Moser. MAE was sold in various forms not only for the KIM-1 and SYM-1 but also for other 6502-based computers including Commodore, Atari, KIM, and Apple and in the Netherlands the Elektor Junior. Other forms of MAE included a cross assembler for 6800 and 8085.
Carl Moser and JR Hall were founders of Eastern House Software, the company that created several products for Atari 8-bit users, including Monkey Wrench and Monkey Wrench II, and the KISS word processor.

On topic on this site are the preserved KIM-1, SYM-1 and Elektor Junior versions. I have binaries, manuals and (reconstructed) sources for these versions for download.

Note that the manuals for the SYM-1 RAE are well written, and a good addition for the manuals of MAE.

On this page:

Catalogs and flyers Eastern House Software

Eastern House Software Catalog

Eastern House Software Dealer Brochure

EHS catalog 1985

EHS catalog

EHS flyer

EHS Gazette 1981-03

PC commandline tools to manipulate MAE/RAE files

To get text into and out of the ASSM/TED program on the 6502 computer to the PC world,one can use several methods.
Written in Freepascal. Sources included, can be compiled in Linux etc.

The first method is using a terminal emulator and upload a text file or catch the output of the ASSM/TED program.
That gives some problems, mostly related to missing line numbers, or too much blanks.

Strip Blanks
The output of ASS/TED to the screen contains many blanks. When you want to uplaod the captured output, those blanks have to go

D:\myfiles\MAE\PC tools>StripblanksMoser.exe
V1.0 Strip blanks from captured ASSM/TED Moser source file
V1.0 Hans Otten, 2024
Syntax: StripBlanksMoser <sourcefile with blanks> <output source file to upload 
to ASSM/TED> [Y]
Y to overwrite outputfile without question asked

Add numbers
When you have a MAE/RAE source file without numbers, you can add those with this utility, increment of 10.

D:\myfiles\MAE\PC tools>AddNumbersMoser.exe
V1.0 Add numbers 0001-9999 to source file to make a ASSM/TED Moser source file
V1.0 Hans Otten, 2024
Add numbers 0001-9999 to ASSM/TED Moser source
AddnumersMoser <sourcefile without numbers> <output source file with numbers> [Y]
Y to overwrite outputfile without question asked

The other method is to dump or upload the text buffer as memory binary dumps.
Text is stored in memory as:
the text
10 test
is stored as:
00 10 20 74 65 73 F3

Converts a binary MAE/RAE file to an ASCII text file without line numbers and normal line end

D:\myfiles\MAE\PC tools>RAEtoTXT.exe
V1.0 Convert a  ASSM/TED Moser RAE memory dump to text file
V1.0 Hans Otten, 2024
RAEtoTXT <sourcefile memorydump> <output text file  [Y]
Y to overwrite outputfile without question asked

Converts a text file to binary RAE format, with line numbers.

D:\myfiles\MAE\PC tools>TXTtoRAE.exe
V1.0 Convert a  text file to ASSM/TED Moser RAE memory dump
V1.0 Hans Otten, 2024
TXTtoRAE <textfile > <output memorydump file  [Y]
Y to overwrite outputfile without question asked

How to dump or upload the the MAE/RAE text buffer


Start ASS/TED and add some lines

C 1979 BY C. MOSER

4163-53FC  5400-5EFC  5F00
4163  5400

>20 lege regel

4163-53FC  5400-5EFC  5F00
4176  5400

Current (4176 in example above is to be stored at D3 (low), D4 (high))

BR to the KIM monitor and save 4163 to 4176 to a file, remember the end address, add that to the filename!

– Start ASSM/TED and BR to monitor
– Load the text file, place the end address in D3 (low), D4 (high)
– Enter ASSM/TED via the warm start at 2003 (KIM-1) or B003 (SYM-1)

Add the Apple 1 monitor to the KIM ROM!

The Apple 1 and the KIM-1 are some of the earliest 6502 systems made.
Both are desirable, Apple 1’s sell for lots of $$$ and KIM-1s are getting more expensive.

Luckily we can build a KIM-1 clone that is either cheap and compatible, like the PAL-1, or a bit more authentic as the various KIM-1 boards.
Anyway, a clone has the KIM ROMs, and in E(E)PROM, to make it a KIM-1 clone. Altering is not done, you loose that unique spartan user interface!

The Apple 1 has also a monitor program, often called Wozmon to honor the genius of Steve Wozniak.

And you can combine both user interfaces on a not expanded KIM-1 clone!
I also included the Wozmon as a Setting in the KIM-1 Simulator.

Read more here!


Wozmon in the KIM-1 clone

The Apple 1 monitor (Wozmon) to be included in the empty space in the KIM-1 tape ROM

The Apple 1 and the KIM-1 are some of the earliest 6502 systems made.
Both are desirable, Apple 1’s sell for lots of $$$ and KIM-1s are getting more expensive.

Luckily we can build a KIM-1 clone that is either cheap and compatible, like the PAL-1, or a bit more authentic as the various KIM-1 boards.
Anyway, a clone has the KIM ROMs, in an E(E)PROM, to make it a KIM-1 clone. Altering is not done, you loose that unique spartan user interface!

The Apple 1 has also a monitor program, often called Wozmon to honor the genius of Steve Wozniak.
And you can combine both user interfaces on a not expanded KIM-1 clone!
Ronny Ribeiro, a user of a PAL-1, saw that the KIM tape ROM has quite some unused space. In a real KIM-1 that is wasted, you cannot program the ROM.
In a clone you can. He saw that that free space is large enough to hold the Wozmon, adapted a bit for the KIM-1 TTY I/O.
He offers a ROM image for a clone, with the Wozmon built in at 1AA0. And added a command to go back to the KIM-1 monitor.
He also replaced the ‘KIM’ prompt in hi system with ‘PAL.

Two versions here, original KIM ROMs in 2K image (00 filler bytes!) with Wozmon in tape ROM empty space (and no change to text in the KIM ROMs)

– wozmon kim rom zp24.bin with zeropage used from $24 as original Wozmon
– wozmon kim rom zpe5.bin with zeropage used from $E5 just below start of KIM-1 monitor zeropage

Start Wozmom at $1AA0, used buffer at $0300

Based upon the ideas and work of Ronny Ribeiro.
Source included. Standard 6502 assembler, I used TASM32

The KIM-1 Simulator is used to test this. And this Wozmon is now available in Settings!

Here I offer you that ROM. I reconstructed the source and added the result to the KIM-1 ROM image. WIthout the KIM prompt change!
In the archive you find source etc of the Wozmon for KIM, the binary ROM image to load in the KIM clone rom, the original Wozmon source and a small userguide by San Bergmans.

Another update to the Simulators

KIM-1 and TIM Simulator have seen a small update.
Improvements on console handling and little annoyances. Focal added as programming language, for KIM-1 and TIM!
The Apple 1 Monitor, wozmon is now available as a Setting to be added the not used space in the 6530-003 tape ROM.

KIM-1 Simulator 1.4.0
TIM Simulator 0.6beta
Convert Hex Formats 2.8 (bundled also with simulators)


Focal-65 V3D for TIM and KIM-1

Focal on the 6502, a page on this small language, originating for Digital Equipment.
A small interpreter (about 5K) for a convenient interpreted language. Floating point 9 digit accuracy. At least two versions were distributed around 1977, one by Aresco, called “Focal V3D” and another by the Program Exchange as representative of the Denver 6502 Group, often called “Focal-65E”

Latest addition is a reconstruction of the source, by Wayne Wall of the Denver 6502 Group in 1977, of Focal V3D for the TIM to binary, and a port to the KIM-1.
Based upon a listing of the TIM Focal-65 from 1977 and a Focal-65 User manual, repaired and cleaned up.
And that enabled the reconstruction of the soource Focal-65 V3D as distributed by Aresco!

Read all about Focal-65 here!


Focal-65 V3D for TIM and KIM-1

Focal on the 6502, a page on this small language, originating for Digital Equipment.
A small interpreter (about 5K) for a convenient interpreted language. Floating point 9 digit accuracy. At least two versions were distributed around 1977, one by Aresco, called “Focal V3D” and another by the Program Exchange as representative of the Denver 6502 Group, “Focal-65″ or FCl_65” or “FCL-65E”

Information from the German 1981 article in MC Magazine, see the articles, indicates the existence and sale of Focal versions by the 6502 Program Exchange:

  • FCL-65 and FCL-65E with Mini userguide
  • My version from Aresco Focal V3D, 1-oct-1977 binary and userguide
  • Focal V3D for TIM, listing known and available on this page
  • Focal-65 V3E 1-oct-1979, Apple II, source listing known at MC Magazine in 1981
  • V4 for Apple, listing known and in possession of Wayne Wall, not public available

I suppose this list is incomplete, other versions may have existed. None but my binary of Aresco Focal-3D, the Aresco V3D Userguide, a User Guide by the Denver 6502 group and a listing of Focal-65 V3D for the TIM survived and is available.

Latest addition to this page is a reconstruction of the sources, of Focal V3D for the TIM to binary, and a port to the KIM-1. Also the Aresco version source is reconstructed and identical to the tape dump of 1978.

On this page you will find:

  1. My experience with Focal-65 as started in 1979
  2. Reference material: User manuals, listings
  3. Magazine articles about Focal-65
  4. Reconstructed sources of Focal-65 for TIM and KIM-1
  5. Reconstructed source of Focal-65 for the KIM-1 Aresco version
  6. On the origin of Focal-65

My experience with Focal-65 started in 1979

In 1979 my good friend Anton Muller, at a meeting of our Dutch 6502 KIM Club, surprised me with a package Anton had imported from the U.S.A. : Focal V3d by Aresco.
The package came with a cassette tape and a user manual. We installed it on the KIM-1 and played with it. Impressive what was done in about 5K!
Floating point, string handling, a trick to suppress the hardware echo of TTY input.
After an article in our club magazine more members of the club became Focal-65 users and published articles about it.

This version of Focal-65 has survived. I have dumped a working version from cassette in 2004 (not the original alas, but a working copy with a bit too much) and scanned the user manual.
Manual and binary version have been available on this website now several years. Also I added DEC Focal manuals, Digital Equipment Corp. developed and sold Focal as a product for the PDP computers. In the KIM/6502 User notes articles were published on making Focal even more interesting, also published here.

When the KIM Simulator became usable, I tested Focal and saw that suppressing the TTY echo worked, but the wait for keyboard input loop preceding the read character routine did not. So I added a setting to let Focal-65 survive that loop. So Focal-65, Aresco version, runs unaltered on the KIM-1 Simulator!

The FOCAL programming language

In 2023 a source listing appeared, thanks to Paul Birkel, of Focal-65, programmed by Wayne Wall and friends in 1977. Target system is a TIM such as Jolt or Superjolt. I typed in that listing exactly with modern assembler syntax and made that version operational.
Here I present several reconstructed versions, for TIM (653-004) such as Jolt and KIM-1 based systems.
– A TIM/Jolt/Superjolt system needs minimum 8K RAM in lower memory.
– The KIM-1 needs memory, minimum 8K, from $2000 and up.
See below for the TIM version and a port to KIM-1. These are 90% identical to the Focal-65 V3D Aresco version, so that was the start to recreate that source too .

Reference material for download

First some downloadable reference material.

DEC-08-AJAB-D PDP-8-I FOCAL Programming Manual.
Focal by DEC is the beginning of all Focal implementations. A typical DEC manual, easy to read, complete, well organized.
DEC-08-AJBB-DL Advanced FOCAL Technical Specification April 69
This manual is where Wayne Wall got his design. From the flowcharts and labels, similar names and concepts can be found in the Focal-65 source
Focal-65 users guide V3D, by Aresco
Focal-65 Users Guide V3D by the Denver 6502 Group.
Cleaned up version made by me.
TIM Focal-65 V3D source listing
Cleaned up version made by me.

Articles on Focal-65

KIM/6502 User notes
Articles from the magazine, Focal corner

  1. Introduction to FOCAL, 6502 User Notes 12
  2. Improve on echo problems with KIM TTY, 6502 User Notes 13
  3. Make room for enhancements, extend to 8K, User Notes 14
  4. Speed it up, 6502 User Notes 15
  5. Cassette save/write an LED display listing, 6502 User Notes 16

KIM Kenner
Introduction to FOCAL, how to program, Dutch

Compute II
Modify and Move FOCAL 65-E into EPROM, Compute II Issue 3

MC Magazine
German article on Focal-65, has interesting information on versions

Working versions, reconstructed from sources

Denver 6502 Group Focal for TIM

In 2023 a listing of Focal-65, by Wayne Wall, for a Focal-65 version for the TIM, showed up, thanks to Paul Birkel.
A low low quality scan, so I cleaned it up, improved contrast, removed artefacts and cropped it. The result is readable, but not fit for OCR.

TIM Focal-65 V3D source listing
Original printed listing 1977 by Wayne Wall. Cleaned up version.

I typed this source in, exactly as the listing: uppercase, same comments, same line numbers.In this way I honor the original author and also enable checking of the binary result.
I did change the assembler syntax to a modern assembler. The original was written for PAL-65, an assembler by Wayne Wall in PDP macro assembler format.
When it assembled I compared the binary out to the binary in the listing by hand. Of course typos and the curse of direct addressing, the #!, caused some extra work.
The result was a binary with the same length. as shown in the listing.

Then the binary was loaded in my TIM Simulator, with a small external patch for the ‘no echo’ input character routine in the source. The TIM has ‘software echo’ hardcoded in the monitor for reading a character from TTY, so the monitor code is copied with optional echo.
It runs!

Focal-65 for the TIM, here the source as typed in, listing, binaries in Intel hex and Papertape format and the TIM Simulator patch.

Denver 6502 Group Focal for the KIM-1

To illustrate how easy it is to adapt Focal to other 6502 systems, I ported the TIM version to the KIM-1.
Changes required:

  1. Program moved from $1000 to $2000
  2. Replaced the TIM I/O package with a KIM-1 version: IRQ/BRK vector, no echo character input (partly taken from the Aresco disassembly for character output
  3. Further no changes, same line numbers, same size

This version runs fine in the KIM-1 Simulator with the Focal V3D setting.

Focal-65 for the KIM-1, here the source as typed in, ported to KIM-1, listing, binaries in Intel hex and Papertape format

Aresco Focal-65 V3D

Here the original Aresco Focal V3D dump from cassette. Note that the dump contains a bit more than necessary. The zeropage is completely dumped, and filled in by a running Focal session.
It runs on a KIM-1 and on the KIM-1 Simulator with the Settings – Type of Break setting set to Focal V3D.

First attempt to get a source, unfinished, does not assemble, but informative.
Disassembled source by Paul R. Santa-Maria (2004) and Hans Otten (more comments) (2022).

Focal-65 users guide V3D, by Aresco

Reconstructed source of Focal-65 for the KIM-1 Aresco version

With the source of the KIM-1/TIM and the binary of the Aresco version I have since 1978, it was an easy job to reconstruct the source of the Aresco version.
By comparing the binary output of the assembled source and the binary of the tape, differences can be seen and fixed in the source.

The interpreter code is 100% identical to the tape dump (minus the extra unused bytes saved at the end). Zero page is clean.

The code runs in the KIM-1 Simulator with the Focal V3D setting. No surprise, the binary of the tape dump also runs and the binaries of the code are identical.

Focal-65 for the KIM-1, Aresco version, here the source , listing, binaries in Intel hex and Papertape

The history of Focal for the 6502

Excerpt from the history of the Denver 6502 Group.
In 1975, Denver was a hotbed of computer activities. There was a new computer club called the Denver Amateur Computer Society (DACS), and every meeting was packed with radio amateurs and hobbyists anxious to learn about this exciting new technology. DACS was dominated by Intel 8080 based computers, but there were a few people interested in the 6502. Wayne Wall was one of the first to appreciate the power and speed of the 6502, and he decided to form a subgroup of DACS for 6502 users.

Wayne was a genius assembly language and systems programmer who worked at the Colorado School of Mines. He began holding meetings every Tuesday night at the School of Mines Computing Center for anyone interested in the 6502. At first it was called the 6502 sub-group of DACS, but as time went on, it became the 6502 Group.

All told, there were probably about 100 members, but on a typical night, 30 to 40 people would crowd into the meeting room, anxious to hear Wayne’s latest ideas and see his demonstrations. He was famous for his magic shows that invariably consisted of doing something hitherto unimaginable like simulating human speech with 13 bytes of assembly code. Wayne quickly gained the well deserved reputation as a computer wizard.

Most members of the group owned Digital Group systems. The Digital Group was a local company that had a short but spectacular career manufacturing computer kits. They were powerful, easy to assemble and way ahead of their time, with memory-addressable video cards, system monitors and relatively large memory boards. In addition to the Digital Group systems, the group had a scattering of Kim’s, Tim’s, Jolt’s and even a few odd homebrew machines.

At the time, there was virtually no software available for the 6502. All programs had to be tediously hand-assembled and typed into the machines. Wayne decided that his first task was to find a way to deal with this problem.

The School of Mines had a huge black mainframe called a PDP-10, and Wayne wanted to use the power and capabilities of this computer to write 6502 code. The first possibility was to use a FORTAN cross-assembler that was available from MOS Technology, but it was slow and buggy. Instead, Wayne chose to write 6502 macros for the PDP-10’s “PAL” assembler. After a few days work, Wayne had a fast new assembler that he called “PAL-65.” Suddenly we had the ability to write relatively large assembly language programs for the 6502.

Initially, Wayne cranked out a series of assembly language games. The first was a simple text based game where you shot arrows at a mythical beast called a Wumpus. Most of our computers had between 512 and two kilobytes of memory, but as Wayne’s games grew in complexity, we struggled to keep up, spending our nights soldering memory chips onto circuit boards.

Wayne now turned his attention to a high level language. The Intel based microprocessors had a version of BASIC written by Microsoft. Wayne decided that we should have a similar language, and he chose to write a version of the DEC language called FOCAL. Even though it was a relatively obscure language, FOCAL had some subtle advantages over BASIC, the biggest was its ability to evaluate strings as expressions.

Wayne wanted FOCAL to be a group project, and one evening he showed up with a stack of photocopies of the DEC flowcharts for the language. His plan was to assign each section of the chart to one of the 6502 Group members. We were supposed to go home, write 6502 assembly code for the section, and in a few weeks, we’d have an operating version of FOCAL. Unfortunately, Wayne had overestimated our skills. Most of us had been assembling code by hand and had no idea how to work from a flow chart. In the end, Wayne and Bob Ulshafer did most of the coding.

When it was finally finished, FOCAL was a big breakthrough. Suddenly we had a true programming language. Complex new games began to appear on our computers including a version of the famous mainframe game Star Trek, written by Larry Fish. Over the next few weeks Wayne wrote a five-byte floating point package for FOCAL based on a Dr. Dobbs article. With the new floating point power, simulations and mathematical programs sprouted up everywhere.

With thanks to Paul Birkel for the scan of the listing.

End of year updates to my programs

I have made some small updates to four of my programs.
Updates are bugfixes, cosmetic changes to also to let Raspberry Pi OS versions work, a nicer looking Windows setup and in general bringing all the programs to the same level.

Convert 8 bits hex formats V 2.7
KIM-1 Simulator V 1.3.9
TIM Superjolt Simulator V 0.5
SerialTester V 1.1


Tiny Basic

Tiny Basic for the KIM-1 and the TIM in the Superjolt

Tiny Basic interpreter Copyright 1976 Itty Bitty Computers, used by permission

Tiny Basic on the Superjolt

On this page information how to run Tiny Basic, by Tom Pittman, for the KIM-1 or a TIM (RRIOT 6530-004) based machine, like Jolt and Superjolt, with 4K RAM at least extra.
Any 6502 machine with character I/O can run Tiny Basic, source is available with just a few changes to be made to I/O, memory layout and breaktest. Note that most of the zeropage is used by Tiny Basic!

All tests and binary file manipulation with Tiny Basic have been done with my KIM-1 and TIM Superjolt simulators.
File conversion between binary and papertape and such is done with the Convert Hex 8 bit formats utility.

On this page you find:


The KIM-1 family

The KIM-1 is one of the first computer systems build around the 6502 microprocessor, somewhere in 1975.
The hardware and software concepts in the KIM-1 were reused in a number of systems created later.

  • Application and expansion connector
  • KIM-1 monitor software in ROMs 6430-002 and 6430-003
  • RRIOTs in 6530 (equivalent to 6532)
  • Bitbanged serial interface
  • 6 multiplexed seven segment LEDs and hex keyboard
  • MOS Technology papertape format load and save
  • KIM-1 audiotape format

Over the years I have collected a ‘family’ of small computers with one or more concepts of the KIM-1, as shown in the figure above.

System          Connectors KIM-1 monitor Serial  LEDS + keypad Papertape KIM-1 audio RIOT
KIM-1                X           X         X           X          X           X        X
SYM-1                X           X         X           X                      X        X
AIM 65               X                                                        X        X
MCS Alpha 1                                X           X                      X        X
Elektor Junior                             X           X                      X        X
KIM UNO                          X                     X          X                    X 
Micro-KIM                        X         X           X          X                    X
KIM Clone                        X         X           X          X                    X
PAL-1                            X         X           X          X           X        X
MOS Reproduction     X           X         X           X          X           X        X
KIM-1 Simulator                  X         X           X          X                    X

Me and my KIM-1

My first computer is a KIM-1. Still have it! A life changing experience!

This is the story of me and the KIM-1.

Philips educational kits.

As a young child, at age 12, I was introduced to electronics with the Philips electronic kits. First a Pionier crystal radio. Easy to build, good instruction manual. Lots of listening pleasure!.

Two years later I bought the Philips EE8 Electronic Engineer kit. Again nice builds (the 8 stands for 8 experiments), with a good manual. Since the manual covered the expansion to the EE20 for 20 experiments, I bought the parts myself one by one at Aurora Vijzelgracht, Amsterdam.
More on the Philips electronic kits.

Radio Bulletin

In 1978 I bought my first computer, a KIM-1. It turned out to be a Rockwell rebadged Rev F Mos Technology board.

The beginning of lots of fun, learning, member of the KIM gg Club and making and publishing in the dutch electronics magazine Radio Bulletin and the KIM Kenner.

In 2014 the big KIM-1 machine was finally taken down in parts, the following photos showed the end result as in 1985 after many years of tinkering.

The KIM-1 system ended as a real production system until 1985, mainly to write articles, all Radio Bulletin and KIM Club Magazine related work was done with this system.

My KIM-1 workplace in 1979, no video terminal, no printer, hand assembly

My workplace setup in 1982: KIM-1, dual cassette, tv monitor, H14 printer, ASCII keyboard

1984, VT100 as videoterminal, what a progress!

Then a CP/M machine took over (a Spectravideo X’Press 738) with the same VT100 as terminal.

  • KIM-1
  • 8K RAM  in system case
  • 32K RAM in expansion case
  • Two ACIA 6850 serial
  • A PIA/VIA card with two 6820 PIA’s
  • Parallel ASCII keyboard with home made logic circuit
  • Video Display 32×32 uppercase characters on an analog TV
  • Dual cassette tape system with motor control
  • MDCR digtal cassette system in second expansion case
  • Radio Grafisch Display in second expansion case
  • Heathkit H14 matrix pinter, serial with RTS handshake via bitbanging RIOT port
  • VT100 Digital Equipment Video display unit VT100
  • Boot tape to load device drivers and Micro Ade (extended to 8K)
  • MICRO ADE assembler/editor, used for program development and article authoring
  • Microsoft Basic KB9 (not used often, nice study material!)
  • Pascal-M compiler and interpreter (mainly development and experiments, not for production)

First the KIM-1, I still have it, in working condition, in my private museum. Changes still visible, are a red acryl cover over the LED displays, a capacitor moved to the back to make it flat enough to fit the case I made and some supports to have it lay stable and safe on a table.

Why a KIM-1?

In 1977 I was reading in the electronics magazines about the revolution taking place: 8 bit microprocessors!
During my study I encountered Digital Equipment machines, PDP-8 in the lab, PDP-11 in the Mathematic Computer Science department, a Minc in Medical Physics group, my major.
The electronics department where I was doing an intern not only introduced to digital electronics and I helped them to introduce the Z80 to the instruments designed for laboratory experiments.
I learned assembler quickly, PDP-11 was a dream come true, the Z80 a bit of a nightmare but you could do so much with effort.

At the same time I started to write for the magazine Radio Bulletin, simple analog and digital circuits and continued to be an editor until 1987. I met Dick de Boer who was writing his famous Microprocessor articles and introduced the KIM-1 to the Dutch electronic engineers. So a KIM-1 with the very attractive 6502 was the logical choice for my first microprocessor system.

First case: memory, connectors, power supply

A KIM-1 itself was fun to learn with, but it quickly needed more; a permanent power supply, protection, easy to access connectors and interfaces for  a bus to have  more memory.
So the case seen in the next figure was built:

Power hungry, so lots of lineair power supplies with large cooling.

The first case I built from alu profiles contained the KIM-1, a backplane for 6 memory boards, a lot of power supplies (lineair, so heat was a problem!), a patch panel to access the expansion connector, cassette I/O, serial interface and various switches.

PCBs handmade, double sided!

Memory 2K RAM Card, BEM Bus Brutech Variant made by Hans Otten
Memory boards were made myself by drawing with Edding ink on the blank PCB, etching and drilling. Filled with 2102 RAM IC’s for 1K per board, it filled lower RAM of the KIM-1 $0400 – $13FF. The bus is a 31 pin DIN connector, based upon the BEM (Brutech) bus.

I bought two of this deck from Radio Service Twenthe, Den Haag, fascinating electroncis dump store!

The next thing I built was a video display unit. All TTL 74XX logic IC’s, a 2513 character generator, a AY-5-1013 character generator, an ASCII keyboard, display on TV 32×32 characters uppercase. RS232 input/output to the KIM-1.
On top of the VDU a dual cassette deck is shown. From the famous Dutch dump shop Radio Service Twente two audio cassette decks were bought, some audio amplifiers and power supply added, and a remote control circuit via a 6532 GPIO line (standard as in Micro Ade). Served me well for many years, in 2014 the decks strings were dried out and crumbled after many years of not being used.

Next was a real expansion cabinet with a long backplane for 32K memory with 8x 4K RAM card, 2114 based, Designed by me, published in Radio Bulletin and sold by Visser Assembling Electronics. BEM bus compatible.

4K SRAM card

4K SRAM card, Radio Bulletin September 1979 part 1  part 2

Production 4K RAM card

Prototype 4K RAM card, also hand drawn on the PCB!

In the expansion cabinet three slots were added for I/O. Two cards were designed by me and published in Radio Bulletin: an ACIA card for two 6850 Motorola ICs, and a PIA card for two PIAs, 6522 or 6520 or 6820 or 6821. I never used more than one ACIA and one PIA card. Shown are the prototype cards, in the article production quality PCBs were used.

PIA and VIA card design by Hans Otten June 1984 Radio Bulletin

ACIA Motorola 6850 by Hans Otten, 1983 Radio Bulletin

On one of the ACIAs a VT100 Digital Equipment terminal was connected, taking over from the bit banged serial interface and the homebuilt video display. ON the other ACIA a Heathkit H14 matrix printer was added, a mediocre but adequate printer.

Together with Micro Ade as assembler and editor, the dual cassette deck, 40K RAM In total, this was a nice machine! Until 1987, when I bought the Spectravideo X’Press 738 MSX and CP/M system, used for all my publishing activities.

A third expansion cabinet was built around 1983. It was driven by the PIA’s, the Radio Bulletin Grafisch Display was inside the cabinet, along with two MDCR Philips Digital cassette recorders, alo published in Radio Bulletin. The speed difference between Hypertape audio cassettes and 2400 baud MDCR speed was not that impressive.

Dirk Dral

EPROM card (Dirk Dral)