A-ONE

These page is about the A-ONE family of Apple 1 replicas.

My Apple 1 (replica!) and the A-ONE PLUS

My A-ONE collection

In 2006 Franz Achatz designed the hardware of an Apple 1 replica named A-ONE and sold these for some years. In 2025 Franz continued the product line with updated A-ONE computers.
The A-ONE 2025 products are for sale at the RRU products shop.

The A-ONE was announced as follows:
The A-ONE is a compact and high quality Apple 1 replica made and designed in the Netherlands by Achatz Electronics. Similar, but not identical to the Apple 1 Replica 1. Advantages are the small board size and low IC count,, 50 Hz and 60 Hz rock solid video, and the real Apple 1 slot.

The A-ONE follows the usual concept of Apple 1 replicas. The computer part, the 6502 CPU and 6821 PIA are identical to the Apple 1. The video terminal part is replaced with one or mee modern microcontrollers. In 2006 the Atmel IC’s were the best in the market, so these were chosen for the video terminal.

Franz asked San Bergmans to develop the firmware for the video terminal part with an ATMega32 . And Ben Zijlstra for the PS/2 interface with a ATTine2313.
San Bergmans also developed a subset of his big PC based SB Assembler, the A1-Assembler, that runs on the 6502.

In 2006 I acquired the A-ONE EXTENDED. In 2026 the A-ONE PLUS and standard board were added tot he family.

The A-ONE family in 2006

A-ONE Standard board
A-ONE EXTENDED
A-ONE Prototype board
A-ONE Prototype board with breadboard

The A-ONE family in 2025

A-ONE standard board
A-ONE EXTENDED
A-ONE PLUS
A-ONE Cassette Interface
A-ONE Prototype board
A-ONE Prototype board with breadboard

Specifications of the A-ONE
All A-ONE computers share the same design, firmware and software.

CPU: MOS TECHNOLOGY 6502 (65C02 supported)
System-Clock: 1 MHz
RAM Memory: 32KB SRAM
ROM Memory: 32KB (64KB EPROM, selectable are two banks)
Video: 40 Chars/line at 24 Video-lines 50Hz and 60Hz
Video Out: Composite positive Video, 75 Ohms
Keyboard: PS/1 Keyboard interface
RS232: 9-pin SubD Female, 2400 Bd
Expansion: 2×22 Edge Connector (3x for EXTENDED and PLUS
Powersupply single universalAC-DC Adapter DC 9-12VDC
Supply Current: 250 mA
2025 versions: USB connector as alternative power supply
Software
WozMON monitor
Apple 1 Basic
Krusader 1.2 Assember/Editor
A1-Assembler
Jumpers for:
JP1: Video 50/60Hz
JP2: MemoryMap (see Manual)
JP3: H-A14 = 65C02 CPU, A14-L = 6502 CPU

A-ONE 2006 standard board
This is the first edition of the A-ONE. All other A-ONE computers share the same design.
A compact 100x160mm PCB, professionally made.

A-ONE 2006 EXTENDED
This larger PCB adds a breadboard area to the A-ONE, access to all the relevant signals in the system and three expansion slots.
And with the extra USB powersupply connector.

A-ONE 2025 Standard board
A remake of the standard board. Black PCB, USB power connector added. 3d printed supports.

A-ONE 2025 EXTENDED
Also a remake of the EXTENDED version. Same specifications, black PCB, 3d printed supports.

A-ONE 2025 PLUS
A new family member. An A-ONE EXTENDED with a mini PS/2 keyboard placed on a plexiglas bottom, with 3d printed supports.

A-ONE Cassette Interface
The A-ONE cassette interface is compatible with the ACI Apple 1 casssette interface.
With different components, like a GAL16V8, a 27512 EPROM and a LM311 comparator. The software on the EPROM interface, at c100, behaves identical.

A-ONE prototype boards

Working with the A-ONE extended becomes even more a pleasure with the prototype boards sold by Achatz Electronics.

Since the Apple 1 connector is electrical equal to the A-ONE but of different size, it is possible to use the Apple 1 and Replica 1 extensions, such as the CFFA1 and the multi-I/O board on the A-ONE. It will need a A-One slot to Apple 1 slot interface, one on one, perhaps via one of the prototype boards.

A-ONE information

A-one

A-one extended

	A-ONE manual 1.0
	A-ONE manual 1.10
	A-ONE manual 2025
	Elektuur announcement
	A-ONE flyer
	A-ONE terminal description by San Bergmans

SB-Projects, San Bergmans’ description of the working of the Apple 1 and all about the A-ONE

Downloads

Proton PIM-1

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PROTON Electronics: PC-1, CB80, PIM-1

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EMUF 6504 remake

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MACH-9 MMS Inc 6809 CPU Plug-in for AIM 65

Royce Taft has a MACH-9 MMS Inc 6809 CPU Plug-in for AIM 65 and reverse engineered it. He sent me his design to be pu...

Replica 1, first version

The first Replica 1 is just called “Replica 1”.

The Replica 1 is as simple as can be, to make an Apple 1 look-a-like. CPU (65(C)02), SRAM (62256 32K), EEPROM 28C64 8K), clck (1 MHz can oscillator) is as expected, as is the 6821 PIA for I/O.
Keyboard input is original also, just an ASCII parallel keyboard, like the Apple 2 keyboard.

The video circuit, quite complicated in the original design, is replaced with a programmable ATMEGA8 with a 74LS166 shift register.

As an extra and optional a serial I/O board for Revision C is used to also allow a PS/1 keyboard as keyboard input. Made with a ATMEGA8515. The serial I/O board can also be used on the original Apple 1! There was also a Revision B with the serial I/O integrated on the main PCB, see the photos below.

The Apple 1 expansion slot is replaced with a 40 pin connector, with the same signals at the same position but mechanically incompatible with the Apple 1.

The WOZmon monitor and Apple 1 Integer Basic are burned into the EEPROM.

The announcement by Vince Briel on Applefritter in 2005:

The Briel Computers Replica 1 is a fully functional clone of the Apple 1 © computer created by Steve Wozniak in 1976 that started Apple Computers ©. The Replica 1 is available as a kit that you solder all the components onto the circuit board, or preassembled.

A new circuit layout was done to implement a more simple circuit and replace older no longer available IC’s. This new design allows for a smaller board yet still gives all the functionality of the original design. Just like the Apple 1, the keyboard and power supply are not included. Simply add your own PC 386-Pentium© class power supply, a composite TV or monitor and a PS/2 keyboard or Apple II© style ASCII keyboard and you are set.

The serial I/O board is a unique design made to work with both the Replica I and the Apple 1. It is a piggy-back board that goes in the 6821 socket and is transparent to the computer. With this design anything that goes to the video display is sent to the serial I/O board and anything that comes in through the serial I/O is treated like a keystroke. This method reduces the speed of the I/O board to 2400bps but gives the advantage of being able to save BASIC programs as a text file. No setting switches or running software required. Just install it, set up Hyper Terminal, connector your serial cable (not included) and your all set.

Revision B

	Replica 1 Setup and Users Manual Revision C January 2005
	Replica 1 Serial I/O board Setup and Install Manual January 2004
	Replica 1 Circuit Diagram
Replica 1 firmware source	Replica 1 keyboard encoder Video Rev C Serial I/O

Hardware bug

There is a hardware bug that may occur on the replica 1 boards. It causes occasional dropped characters from the display. There is a fairly easy fix but it does require soldering.
Requirements: .01uF ceramic disc capacitor, soldering iron (25W preferred) and solder.
Locate the chip labeled 74LS04 on the circuit board. Pin 3 is on the side that is closer to the edge of the board. Pin 14 is on the other side of the chip top pin.
So, the pins are labeled as follows:

|(74LS00 is here on the board)
|
|
|74LS04
|
|__8_____7
|__9_____6
|_10_____5
|_11_____4
|_12_____3*
|_13_____2
|*14_____1
|
|----- this is the edge of the board
|
|----------- 6821 is here on the board
|

Pin 1 and 14 are closer to the 6821. Connect the ceramic capacitor on the bottom of the board to pins 3 and 14. Make sure the capacitor doesn’t touch any of the other pins on the chip. This will eliminate all dropped characters.

Revision B has the serial I/O on the main PCB

Proton PIM-1

Gerben Voort acquired a microprocessor development system PIM-1 developed by Proton, of PC-1 fame. Here his photos of...

PROTON Electronics: PC-1, CB80, PIM-1

PROTON Electronics, a small company from Naarden the Netherlands, led by James Post, and A.J. Kool as technical manager,...

EMUF 6504 remake

A remake by Klaus Loy of the 6504 based EMUF 6504 as published in MC, see the many original articles about the EMUF. ...

MACH-9 MMS Inc 6809 CPU Plug-in for AIM 65

Royce Taft has a MACH-9 MMS Inc 6809 CPU Plug-in for AIM 65 and reverse engineered it. He sent me his design to be pu...

Replica 1 Briel

The beginnings
In 2003 Vince Briel, working with Tom Owad, got the idea to design an Apple 1 replica. He looked at the Apple 1 circuit and took the easy parts: the 6502 and 6821, RAM, ROM.
The difficult part is the video circuit with hard to get parts and replaced that with a ATMega processor. He also added a PS/1 keyboard input and combined that with the parallel keyboard input circuit. The result was a functional replica of the Apple 1 on real hardware.
Vince then started Biel computer selling Replica 1 kits and assembled boards. Many revisions followed, hundreds were sold. The latest incarnation, the Plus, is still for sale, not by Vince who stopped in 2015, but by ReactiveMicro, also for sale there the CFFA1 mass storage card.

My experience with the Replica 1 begin with the Replica 1 SE in 2007, the same period Vince made the Micro-KIM

What you can find here: