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 kits on my website dedicated to 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)

Original KIM-1 ROMs reproduced

I have two sets of KIM-1 ROMs. One set is the original KIM-1 dump by Dwight Elvey, in which the filler bytes (unused locations in the ROM) are filled with $00.
Alas the dumps by Dwight have a couple of bit errors and the NMI vector is wrong.

The other set is the result of assembling the source in which the assembler used $FF for the filler bytes. It makes sense to use $FF, since EPROMs can be programmed byte for byte ‘1’ later to ‘0’s.
Functionally the filler byte is irrelevant, so I present here the ROMs with filler byte 00 (corrected Dwight original KIM-1 dumps) and filler byte FF (assembly result).

6530-002 $1C00-$1FFF, filler bytes $FF 6530-002 ROM
6530-003 $1800-$1BFF, filler bytes $FF 6530-003 ROM

6530-002 $1C00-$1FFF, filler bytes $FF 6530-002 ROM
6530-003 $1800-$1BFF, filler bytes $FF 6530-003 ROM

Corsham Bus Extender

Corsham Technologies produces a Bus Extender fot the KIM-1. SImple but so handy.

It is placed beween the external device on Application or Extension Connector and has 44 pin header to attach wires to a breadboard for example.
Only negative I can say about it, tinned edge connectors and not gold plated.

Nice addition to my Reproduction KIM-1s!


Ruud Baltissen: Build a KIM-1

Ruud Baltissen started the whole KIM-1 Replica world by publishing a page many years ago about Building a KIM-1
All replica’s, from the MICROKIM to the Nachbau followed his design.

Replicated here the are relevant text and schematics by Ruud.

Build a KIM-1

The goal of this project is to rebuild the KIM-1. This isn’t “Just take the schematic of the KIM and go ahead!”. The KIM-1 uses two 6530s that are custom ICs and therefore cannot be bought in any shop. This project uses replacement parts.
The troubleshooter: 6530
As said, the KIM-1 has two 6530s on board. For more info about this IC, please read about the 6530 here. Anybody who is a little bit familiar with the hardware market can tell you that you cannot buy the 6530 as a regular part. And the 6530 is a custom IC: Commodore made various types but all were branded 6530. For example, the 6530 found in the CBM 4040 drive is different from the ones of the KIM. Even the two 6530s of the KIM itself are different: in this case it is the content of the builtin ROM.
Happily enough there is another IC available that can be used as replacement: the 6532.

The 6532 has 16 I/O lines, an internal timer and 128 bytes of RAM onboard, but no ROM. For this project we’ll use an external EPROM as replacement. The pin out of the 6532 is completely different but that should not be a problem.
Another difference is that a 6532 has pin PB6 available where a 6530 hasn’t. See it as a bonus as I haven’t found any reason how it could jeopardize our project.
The 6530 can generate a IRQ but in case of the KIM-1 this feature isn’t used. The main reason is that pin PA7 is needed to output the signal and it is used for other things. The 6532 has a separate IRQ output. I used two jumpers, J54 and J5, to enable someone to use this function if needed.
The last and major difference however lays in the way the registers are selected:

function:       RS:  A6:  A5:  A4:  A3:  A2:  A1:  A0:  R/W: 
RAM              0    x    x    x    x    x    x    x    x   
DRA              1    x    x    x    x    0    0    0    x     A
DDRA             1    x    x    x    x    0    0    1    x     B
DRB              1    x    x    x    x    0    1    0    x     C
DDRB             1    x    x    x    x    0    1    1    x     D
PA7, IRQ off,                                               
      neg edge   1    x    x    0    x    1    0    0    0     F
PA7, IRQ off,                                               
      pos edge   1    x    x    0    x    1    0    1    0     G
PA7, IRQ on,                                                
      neg edge   1    x    x    0    x    1    1    0    0     H
PA7, IRQ on,                                                
      pos edge   1    x    x    0    x    1    1    1    0     I
read interrupt                                              
       flag      1    x    x    x    x    1    x    1    1     E
read timer,                                                 
       IRQ off   1    x    x    x    0    1    x    0    1     J
read timer,                                                 
       IRQ on    1    x    x    x    1    1    x    0    1     K
Clock / 1,                                                  
       IRQ off   1    x    x    1    0    1    0    0    0     L
Clock / 8,                                                  
       IRQ off   1    x    x    1    0    1    0    1    0     M
Clock / 64,                                                 
       IRQ off   1    x    x    1    0    1    1    0    0     N
Clock / 1024,                                               
       IRQ off   1    x    x    1    0    1    1    1    0     O
Clock / 1,                                                  
       IRQ on    1    x    x    1    1    1    0    0    0     P
Clock / 8,                                                  
       IRQ on    1    x    x    1    1    1    0    1    0     R
Clock / 64,                                                 
       IRQ on    1    x    x    1    1    1    1    0    0     S
Clock / 1024,                                               
       IRQ on    1    x    x    1    1    1    1    1    0     T

In total 5 address lines are used, meaning 32 registers. But 11 of the 19 registers have one or more mirrors.

Read:          J E J E         K E K E         J E J E         K E K E 
Write:         F G H I         F G H I         L M N O         P R S T 
R/W:           A B C D         A B C D         A B C D         A B C D         

As we can see, the last 16 registers equal the 16 of the 6530 itself. So now we have to develop some logic which will do the following:

  • The I/O of the 6532 is only visible within a range of 64 bytes
  • The first 16 bytes represent register 16 to 31
  • The next 48 bytes are mirrors of the first 16
  • Only 64 bytes of RAM are used


  • Input A6 won’t be used and can be tied to GND
  • Input A4 is connected to address line A4 of the 6502 via a NAND gate.
  • The second input of that NAND gate is connected to the /CS2 input.
    The idea behind this is simple: The moment that the I/O part of the 6532 is selected, the NAND gate outputs a (H) thus selecting the wanted last 16 registers. If needed, the user can select the other 16 registers as well by connecting the second input of the NAND gate to +5V.
  • A 74LS138 enables the /RS and /CS2 lines at the right moment.

Here we have a luxury problem. We only need 2K of (EP)ROM like the 2716. The problem is that the 2716 is hard to find and more expensive then the 2764 or its bigger brothers. When we use a bigger EPROM we could tie the unused address lines to GND.
The same problem occurs with the RAM. In this case I have chosen for a 62256, a 32 KB RAM. This looks like a massive overkill but see later.
If we have to use bigger RAMs or EPROMs anyway, it is quite easy to use other parts of that chip by OR wiring the CS line with more Kx outputs of the main 74145. In case of the EPROM we also can connect switches to the surplus address lines and have the advantage of a multi-KERNAL system.

Extra address range
KIM-1 only supported an address range of 8 KB in the first place. The pin DECEN at the Userport can be used to extend that range but HAS to be connected to GND for the original configuration. The idea is that external cards can use this input to alter the range.
I added an extra 74145, IC7, and two jumpers that enable the user to make a more efficient use of the hardware. Both jumpers, J2 and J3, have to be closed to start with.
If you don’t want to use the 74145 at all, only close jumper J1.

The first thing one can do is to let the binary start at address $F800. Your self built KIM will still behave as usual. Now you can add your own RAM from address $0000 on up to $E000 and the only thing you have to do is remove jumper J2.
If you are only interested in adding RAM, a better idea is to use the original one, IC4, the 62256 32 KB RAM. You only have to remove the jumpers J13..17 and to close one or more pair of pins of jumper block J18. By closing all four pair of pins you make use of the full 32 KB.
Jumper J3 is only needed if you want to expand your self built KIM even further and want to use, for example, the $E000/$FFFF range for (EP)ROM.

Schematics of the new KIM-1

What are the major differences with the original schematic?

  • Replacement of the 6530s by 6532s.
  • Addition of two NAND gates to handle the 6532s.
  • Addition of an EPROM.
  • Replacement of the 6108 RAM ICs by a 62256 or equivalent 32K*8 SRAM.
  • Addition of a 74LS138 to decode the RAM and I/O of the 6532s.
  • The resistor for K6 has been dropped.
  • Addition of jumpers to enable the combination of other K lines.

KIM-1 PAL-1 KIM CLone KIM MicroKIM Reproduction resources

This page is a Work in Progress since November 2022!

The clones of the KIM-1 that appeared the last years have renewed the interest of the retro scene.

Old software is restored or typed in again and adapted to the current use of serial terminal emulators and cross assemblers instead of the hardcopy Teletype interface and native assemblers of the old days.

This site contains a lot of that material already. There I have tried to collect all older original material.

Here a link of current websites with relevant material. As usual, a list of external links always will suffer of bitrot, so please report dead links!

Netzherpes, by Nills. Very active PAL-1 user. Lots of older software newly typed in.

KIM IEC, Dave McMurtrie’s 1541 Routines for the KIM-1

See also the Nachbau KIM-1 IEC/RAM card page.

SD card on PAL-1 masterhit Nils KIM Venture startrek Jim McClahanan

Dave Hassler

PAL- stores/tkoak/

Debug packages
Basic games

Tiny Basic


KIM-1 Computing Focal etc

KIM-1 Computing

PAL-1 Hacks


CC65 pathches

Jeff Tranter

Discussion forum for PAL-1

twitter friends

@LiuGN PAL-1 desigenr/tindie
@masterhit netzherpes
@Devilish_Design (KIM-1 clone)
MOS KIM-1 Reproduction Kit

Bob Applegate Corsham Technologies (Tiny) Basic Examples, Utilities

Focal runs on KIM-1 Simulator

KIM-1 Simulator version 1.1.6 has been published. Get it here.

It now supports Focal-V3D 12-AUG-77 (the Aresco version) from the KIM-1 Software page, see here.

Updates to the Simulator are a working echo suppression (see here for background). Available to any program.

For Focal V3D a setting has to be made in the Settings, to allow Focal to do its magic in the input routine.

By working on Focal I did add comments to the disassembly of what I found. You will find the original by Paul R. Santa-Marie and my partly commented version in the archive.

macOS compiled version of KIM-1 Simulator

Thanks to user hobo of a macOS compiled app is now included.


Tiny Basic

Tiny Basic

Tom Pitman’s Tiny basic. Small enough to fit in the 1K KIM-1, yet a real Basic interpreter

Tiny Basic binaries,
low memory version is tiny3, load address 0000 start address 0200
high memory version is tiny 1 load address 0000 + tiny3 load address 2000, start address 2000
Tiny Basic manual as pdf
Tiny Basic manual as html
Tiny Basic manual as text file
Tiny Basic Experimenters kit as pdf
Tiny Basic Experimenters kit as html
Tiny Basic Experimenters kit as text
Getting the most of Tiny Basic.pdf
Articles on tiny Basic from 6502 User notes
Source of Tiny Basic, monitor, and Tiny Basic Bill O’Neill
Tiny Basic for CC65 assembler sources
Tiny Basic games, such as adventure
Games for Tiny basic from Dr Dobbss Vol 1 Page 1, Page 2
Articles from the dutch KIM user Club:
KIM Kenner 10 Tiny Basic, tips how to save and load and change prompt, Hans Otten.
KIM Kenner 23 Tiny Basic, Filip van Kenhove, adapt to Elektor Junior

1977 01 Tiny Basic a mini language for your micro
kilobaud 1977 12 Tiny Basic
1978 06 Tiny BASIC shortcuts
1978 10 Not so Tiny (Basic)
Tinkering with Tiny Basic

KIM-1 programs by Nils

Nils a.k.a. netzherpes typed in a number of KIM-1 programs to run on his PAL-1, the KIM-1 compatible clone.
Not only does he types them in in assembler, some even by contacting the original author!, tests the programs and also provides source and ready to run binaries or papertapes.
And he draws nice looking cover images!

On his github page he has the most recent versions and adds new programs regularly.
Also checkout his blog!

Here a summary of the programs:

Banner for KIM-1

KIM-1 Banner
by Jim Zuber

Download here!


You have 20 shots to detect a 3×1 ship on a 8×8 grid. The ship can be aligned horizontal, vertical or diagonal.
How to play: Enter the coordinated and fire (Button F). If you hit the ship, the mostright counter will jump to 01.
If you hit all 3 coordinates of the ship, you won, the display will show “dEAd” and the number of shots used.
(c) 1978 Roland Kushnier (orig)
(c) 1979 Jody Nelis (bugfix)

Download here!

Target 1 for KIM-1

Little shooting game for the KIM-1
June 18th, 1979
(C) Fer Weber

Download here!

Target 6 for KIM-1

The 6 column Version of Fer Webers Target1 Shooter Game (
Author Fer Weber
published in KIM Kenner 8 on 18.06.1979

Download here!

Telefonbuch for KIM-1

original title: “Datensuche”
by Herwig Feichtinger
(c) 1981 in Anwendungsbeispiele für den Mikroprozessor 6502

Download here!

Phonebook 2.0 for KIM-1

original title: “Datensuche”
by Herwig Feichtinger
(c) 1981 in Anwendungsbeispiele
für den Mikroprozessor 6502

Download here!

Pocket Calculator for KIM-1

by Siep de Vries, KIM Club The Netherlands

Download here!

Tunesmith for the KIM-1

(c) 1979 Anthony T. Scarpelli
found in micro 6/79

Download here!


a silly small Piano for your KIM-1
KIM Piano
(c) by Peter Engels 1979 *

plays whole notes from C to D
by pressing the buttons 0-F.
Download here!

LEDIP a text editor for the KIM-1

The author of the program, Kiumi Akingbehin, Professor at the Michigan University

Download here!

KIM-1 Dungeons and Dragons Dice Simulator

(c) 29.7.80 Myron A. Calhoun
Manhattan, KS

Download here!

TTY rapid Dump/Load

an extension to M.Gönners hex Loader by Bruce Nazarian

Located in Compute II June 1980
Download here!


‘Bob’ Leedom published another game called Baseball in the KIM user notes issue 16

Download here!


by Gino F. Silvestri
A Simon says game for the KIM-1

Download here!

KIM Venture walktrough

This is a walkthrough of one of the most amazing computer games in history.
KIMventure is a (colossal cave like) adventure game for the KIM-1 that fits in only 1 (ONE) KB of RAM. It offers 24 room to explore with a lot of traps and riddles to solve. It was programmed in 1979 by Robert Leedom with pen and paper (no assembler etc.)

Download here!

Hexpawn – another KIM-1 game from 1978

Download here!


Books for the 6502: KIM-1 and more

KIM-1, AIM-65, SYM-1 and other 6502/65C02/65C816 related books.

A mix of English, German and Dutch books.

On my bookshelf I have quite a collection of books on the 6502 family.

Note that manuals and books that come with systems are shown on the pages of the corresponding system!

Microprocessor Systems Engineering
R.C. Camp, T.A. Smay, C.J. Triska
AIM 65 System 65 parts
6502 Software Gourmet Guide and Cookbook
6502 Users Manual
AIM 65 Laboratory Manual And Study Guide
Anwendunsgbeispiele fûr den Microprozessor 6502
Microprocessor_Fundamentals KIM-1
Best of Micro Volume 1 1978
Best of Micro Volume 2 1979
Best of MICRO 3, AIM 65 SYM-1 KIM-1 part June 1979 May 1980
Compute’s Machine Language for Beginners
Compute’s The Second Book of Machine Language
Programming a Microcomputer 6502
Programmieren von Mikrocomputern CPU 6502 (Skriptum)
How to Build a Microcomputer .. and really Understand It!
Mikrocomputer ohne Ballast
Micro Principles KIM-1 user guide chapter 8
Digitaalschakelen met de KIM-1
6502 Assembly Language Programming
6502 Programmieren in ASSEMBLER
Microcomputer Experimentation with the MOS Technology KIM-1
6502 Machinetaal Subroutines
6502 Assembly Language Subroutines
Microcomputer experimentation with the AIM 65
Machine Language Programming Cookbook part 1
Machine Code for Beginners
Microcomputer Systems Principles Featuring the 6502 KIM
Beyond Games: System Software for your 6502 Personal Computer
Assembly Language Programming
Using 6502 Assembly Language
6502 Machine Code for Humans
Programming the 65816 including the 6502, 65C02 and the 65802
Programming the 65816 including the 6502, 65C02 and the 65802
Forth Programming
Programming the 65816
Programming and Interfacing the 6502 with Experiments
Synertek 1981-1982 Data Catalog
Synertek DataBook 1983
Third Book of OSI
TSC 6502 Games Package 1
TV Typewriter Cookbook
Zaks 6502 Anwendungen
6502 Games
6502 Applications
Advanced 6502 Programming
Fortgeschrittene 6502 Programmierung
Programmierung des 6502
Programming the 6502
6502 Applications book
Programmeren van de 6502
Microprocessor Interfacing Techniques
Microprocessor Concepts and Applications
Publisher: Lab-Volt
6502 Assembler-Kurs für Beginner
6502 Machine Code For Beginners
A low-lvel language for use on the MOS 6502 Microcomputer
6502 Microcomputer Programmierung
Programmieren in Maschinensprache 6502
The Giant Handbook of Computer Projects
First Book of KIM
The First Book of KIM-1 in PDF format
The First Book of KIM-1, part in text format
The First Book of KIM-1 in HTML format
Sources of The First Book of KIM-1 in source and papertape format, Jeff Tranter
First Book of KIM-1 for SYM-1
Rockwell Produktübersicht in deutsch
Rockwell Microelectronic Data Devices Catalog 1979
1981 Rockwell Electronic Devices Division Data Book
1984 Rockwell Data Book
1985 Rockwell Data Book
1987 Rockwell Controller Products Databook