Cassette interface for the Micro-KIM

(information and design by Norbert).

Cassette interface for the Micro-KIM.

With small changes Norbert took the circuit described in the 3rd book of Elektor Junior computer. The +12 V problem he solved taking a LT1073 dc/dc converter to generate this voltage. Everything is working fine: Micro-KIM is connected to the soundcard of the computer to store and reload programs.

N39 is needed because there is not a port present or reachable on the Micro-KIM board, so it takes 1/4 74LS01. With a pullup resistor of 3k9 connect the unused inputs to +5V, so the whole thing will not oscillate.
For the +12 V generation a LT1073 CN8-5 was used. The diagram is shown on page 12 of (5V to 15V Step-Up Converter). It is important to use exactly the values of the resistors (metal oxid series) shown there. The LT1073 CN8-5 is presently still available for 4,20? at . They also have got the LT1073 CN8, but it did not work in this context. The no-load voltage measured at the output of the LT1073 is much higher (arround +40V) than the desired +12V. But with load it reduces to about +11.8 V and remains constant there. A 12V/1W zener diode protects the 12V output of the LT1073.


The KIM Uno, designed and produced and sold by Oscar Vermeulen, is a very simple “open-source hardware” project that started out as a replica of the classic 1976 KIM-1 computer. Later, Apple-1 compatibility and a 6502 programmable calculator mode were added, plus a built-in ‘early 6502 software gems’ collection.
It costs about $10 in commonly available parts (board & parts without case or power supply), but provides a faithful KIM-1 ‘experience’. An Arduino Pro Mini mounted on the back contains all the logic and memory.

I have two versions: the ‘original’ and the later redesigned version, Software-wise the same, with on the top of the PCB room for power connector (GND, +5V or a 9V battery) and a slide switch. , I use them with an USB cable (the blue one of this page) for power and the serial interface provided.

The software already works on the blue pill STM32 or an ESP32, with manual cabling to the keyboard/display and I expect a new version of the PCB for the ESP32.

The software for the serial interface (you really need a good serial terminal emulator, like Minicom or Tera Term) can be used on any Arduino Uno. After power on  it delivers a simulation of the LED display or the real KIM TTY teletype interface (a bit broken in the current version).

All well described on the pages of Oscar and well worth the money for a ‘6502 SBC’ experience or a Cosmac 1802 with a small LCD.

The default serial output: an animated KIM display

Pressing control keys to perform ST and RS key

Press TAB to get into KIM TTY mode. Make sure to select on your terminal Local Echo and CAPS Lock. Read the KIM-1 User manual how the monitor operates.

The Apple 1 mode, fully functional.

Microchess adapted to serial

The Wozniak/Baum disassembler



A program, SerialTester,  a guide and test results.

Also updated Prolific PL2303HXA driver misery solution.


MOS KIM-1 Reproduction

Dave Williams designed, builds and sells on ebay MOS KIM-1 Reproduction boards. A real KIM-1 clone!


MOS KIM-1 Reproduction

Dave Williams designed, build and sold MOS KIM-1 Reproduction boards. A real KIM-1 clone! The goal was to reproduce a KIM-1 as exact as possible.
So the MOS KIM-1 Reproduction board has the same dimensions, same connectors and as much as possible the same components, including the audio cassette interface, 1K RAM with 8 2102 SAM ICs. The keyboard is reproduced with the same layout and looks quite identical. Components types are chosen close the the originals (though the KIM-1s went to many revisions with varying looking components) and placed on the same location.
The CPU is of course a 6502 at 1 MHz crystal clock frequency. The edge (Application and expansion) connectors are physically and logical identical.

Since 6530 RRIOT ICs (the 002 and 003 variant) are not available anymore, the same solution as in the other clones is chosen: a 6532 RIOT with a 2K EEPROM and some logic ICs (3) to get a hardware solution that makes it look exactly the same for the KIM-1 ROM software. The PCB is a new design, not the typical 70ties KIM-1 design.

The result is great: it feels, looks and operates as an original KIM-1. First Book of LIM programs run, Even Microsoft KIM-1 Basic and Microchess run, when additional RAM is connected.

Documents (thanks to Dave Williams!)

MOS KIM-1 Reproduction Board Layout
MOS KIM-1 Reproduction Schematic
MOS KIM-1 Reproduction BOM

I added the Corsham Technologies KIM-1 60K RAM/ROM board and the KIM I/O board, which makes it a great system!

With the MOS KIM-1 Reproduction comes a small edge connector PCB for audio and power connections. Alas no TTY connections and keyboard/TTY switch. On an USB stick the well known KIM-1 documentation (all also found on this site!) and the First Book of KIM programs, as typed in by Jeff Tranter in papertape format, also found here. But as extra the programs as KIM-1 audio files are provided, as WAV files, ready to load into the KIM-1.

MOS KIM-1 Reproduction

Original KIM-1 rev F

MOS KIM-1 Reproduction

Original KIM-1 rev F

Some photos from Dave Williams, showing the KIM-1 Reproduction connected to an audio cassette recorder, a KIM-1 S-100 Motherboard with a RAM card, running Microsoft Basic KB9 and a production line of KIM-1 Reproduction (with a real KIM-1 in the top row!)

My MOS KIM-1 Reproduction will be connected to Corsham Technologies cards: SRAM and EEPROM and I/O card

Corsham Technologies KIM-1 RAM/ROM and I/O board connected to a KIM-1


Convert hex formats V2

A program to convert between hex or binary files for 8 bit systems with a 64K address space.
V2 adds the Wozmon Apple 1 format and allow multipart Intel Hex, MOS Papertape and Motorola S records.


Programming a Microcomputer 6502

Programming a Microcomputer 6502, by Caxton C. Forster, scanned and added to the KIM-1 Articles and Books page for download.



KIM-1 Pascal-M compiler

Finally the KIM-1 Pascal-M compiler is available.

After years of (I admit, intermittent) restauration work from paper, the whole package is available again to load on the KIM-1, now including a cross compiler.


KIM-1 Userguide

Added the ‘user guide’ chapters from the book ‘Microcomputer Principles Featuring the 6502/KIM-1′ as KIM-1 User guide.


Microcomputer Experimenting with KIM-1

Another book scanned:

Microcomputer Experimenting with the MOS Technology KIM-1 by Lance Leventhal.