KIM-1 Rockwell sticker

My KIM-1 came as an Rockwell OEM kit. The Rev F board is made by Commodore MOS Technology, the packaging and manuals are the original MOS Technology books, but Rockwell branded.

The logo on the KIM-1 is covered with a sticker, of course to have the Rockwell logo on the board. But some one was so clever to add essential information and addresses of the KIM-1 monitor.

KIM-1 Rev A Photos

Guido Lehwalder gave me photos of his KIM-1 Rev A. Thanks!
Note the different colors of components.

I added these to the KIM-1 Revisions page.

Rev A, photo by Guido Lehwalder

Rev A, photo by Guido Lehwalder

Tor-Eirik Bakke Lunde a.k.a TEBL created several computer systems with detailed documentation.

The RC-ONE is a KIM-1 clone, inspired by the design by Ruud Baltissen, which can be built in a compact to much expanded format.

TEBL separated functionality into separate boards so that each version would cost only around 5$ per piece instead. It means it’s no longer a single board computer, but if it means more people can build it as a fun project then that’s a plus in my book. The main setup does not include the additional 15 I/O lines due to space requirements, but you can add those back to the system by including the 65K Expansion (in addition to the backplane module) if you want to. If you just want to play around with the system and try your hand at machine language coding, you can get started with the CPU board, UI board and a keypad module.

The whole design is documented on TEBLs github page, from circuit diagrams to PCB design.

The manual is an excellent guide to the system, read that first!

Micro-Professor MPF-1B

New in my collection of SBCs:

Micro-Professor MPF-1B. A Z80 based SBC. Perfect trainer. In very good condition, with Tiny Basic built-in. Complete in original box, Monitor source listing, Multitect powersupply,
German handbook, alas no Basic template.

Works perfect:

More photos here:

Instandsetzung und Nachbau eines KIM-1

Ralf (Ralf02, started a thread on the forum64 called Instandsetzung und Nachbau eines Kim-1 in March 2022.
99 pages further of designs and discussions in the thread, delivered a working KIM-1 that is closer to the original KIM-1 than any KIM-1 replica designed. A great achievement and a well deserved compliment to Ralf!

The work of Ralf is not limited to the KIM-1 replica itself. He also designed a KIM I/O module and a 1541 IEC/RAM/ROM module.
Noteworthy is the replica of the KIM-1 keypad.

Read all about it here!

KIM-1 Replika

Colin Wolf (C. W. (chefkoch) ) posted a thread in 2021 on showing a KIM-1 Replika he had build.
A KIM-1 with the dimensions and layout of the original KIM-1! OF course he used 6532 instead of the 6530-002 and -003, so a ROM was needed. To preserve the layout, this ROM was hidden as daughterboard on the back. The daughterboard also has the extra decoding circuit required for the 6532s. A very elegant solution!

He showed these photos on the post:
Read here more about the design and more photos by Wolfgang Robel.

KIM-1 Nachbau

On the forum I found a thread dedicated to a KIM-1 replica with a twist.
Author is Manfred Langemann (manni), this page is published with his permission.
Read here about the KIM computer which has the following features:

  • A complete 6502 Integrated Development Environment (IDE) for writing assembler source code, including editor, assembler, debugger and EEPROM programmer, see screenshot above.
  • The hardware comes with a 6502 micro-controller, 8 KByte EEPROM, 32 KByte RAM and an I/O interface based on an Intel 8255 PPI (Programmable Peripheral Interface), offering three 8-bit ports. The audio tape interface is realised by an NE565 PLL and the RS232 serial interface is based on a MAX232 IC

Ben Eater 6502 Breadboard computer

A page on the Ben Eater 6502 Breadboard computer.

Ben Eater surprised us with his video hands-on series about a breadboard computer.

In many episodes, Ben showed how to build a very simple 6502 computer. Well explained, well executed. The result is a working computer!
You can either source the parts yourself or buy a complete kit from Ben Eater, see his website.
Make sure you buy quality breadboards.

The design is simple, and looks a lot like the early simple SBC’s on this site, and perhaps Grant’s 8-chip (or 7-chip) 6502 computer on breadboard was part of the inspiration.


Junior Computer ][ update

I reported some time ago about a new based upon the Elektor Junior design, by Jörg Walke, the Junior Computer ][.

Junior Computer ][ Main board

In the meantime the Junior ][ has grown up. A Bus card and an Interface card with a lot of functionality has been designed by Jörg, the software has also been updated with EHBasic and much more.

More information on the Junior ][ Computer can be found on the Vintage computing forum of the German “VzEkC e.V” – a club dedicated to the preservation of old computers and on the Junior Computer][ page.
The design, Gerbers, software is on the website of  Jörg Walke.

Here the foreword by Jörg (the ‘I’ is Jörg!)

In May 1980 the DIY project Junior Computer was presented in the Elektor electronics magazine.
The little single-board computer was equipped with 1 KB ROM, in which the monitor program is located, 1 KB RAM (plus 128 bytes of RAM located in the 6532 RIOT), which, according to the authors, was more than enough at the time.

At the 40th anniversary of the computer, I decided to design a version with all features I wanted for the junior back in the 80s. The result is the Junior Computer ][ described here. It has 8KB ROM and a maximum of 128KB RAM. A additional serial RS232 interface and a simple sound output (as described in Junior Computer Book 2, from page 41) are also added. A 5V plug-in power supply with 2A should be sufficient. If external hardware needs to be supplied with voltage via the expansion connector, 3 Amps is recommended.

In order to be able to address the additional memory, the originally address decoding had to be extended. This is designed in such a way that the compatibility of the computer with the original Junior is preserved. An adaptation of the original monitor ROM to match the new memory location was not necessary.

Like its ancestor, the Junior Computer ][ can be expanded with external hardware via a 64-pin connection. The pin assignment oft he bus was largely retained.
In the new version, the 16 available port lines of the 6532 are available via 20-pin connector instead of a 31-pin connector.
The circuit changes mentioned here were made exclusively by me and expressly without the prior consent of the publisher Elektor, which is hopefully forgivable after 40 years. Of course, all rights to the original circuit design remain to Elektor and the authors.

Circuit diagrams, Gerber files, ROM images and other documents of the Junior Computer ][ (including this description) can be downloaded from .

The computer and all its documents are published under the Creative Commons Attribution 4.0 license.

Junior Computer ][ Interface board

Junior ][ Main board

Junior ][ Interface Card

Junior ][ Backplane



KIM-1 Simulator simple demo

To test my new HDMI 4K USB Video Capture I made two videos. Simulator running on one notebook, the other notebook with the HDMI capture dongle recording with OBS Studio.

Simple program

0200 a9 cd LDA #$CD
0203 8D 00 03 STA $0300
0206 4C 00 1C JMP MONITOR ; KIM monitor