Apple 1

About the Apple 1, and modern clones like the A-one and the Apple 1 replica.

All of us older computer geeks know that before selling Macs, Apple founders Steve Wozniak (the genius) and Steve Jobs (the greedy business man) had a lot of success with the Apple ][ or Apple 2 or Apple ii, whatever marketing tricks were done with the name of that remarkable personal computer. The 2 in the name suggest there was an Apple 1 and yes, there were a very limited numbers of boards sold (200 or so, 50 or so survived time, so its a valuable collectible) branded Apple 1 in the 1976-77 time-frame. It has video on board and accepts input from a full size keyboard, so it is one of the first standalone hobby/personal computers based on a microprocessor, the 6502 of course, being powerful and cheap at that moment.

What is an Apple 1?

Besides being the first product of Apple Computers and designed by Steve Wozniak, the Apple 1 featured as one of the first a complete computer, with keyboard and video, on one board, based on an affordable and powerful microprocessor, the 6502.

Apple 1 replica

Apple 1 specifications

(Specifications from from the original manual)

In fact the Apple 1 is made up of:

  • A 6502 based microprocessor system with 4K RAM (dynamic ICs) and 256 bytes ROM
  • A ‘monitor’ program
  • A video terminal, made with dynamic shift registers, a uppercase only character generator (the famous Signetics 2513)
  • Connector for parallel ASCII keyboard

The microprocessor and he terminal part are glued together via a PIA 6821. One 8 bit parallel port reads the ASCII keyboard, the other port delivers the characters to be displayed on the video terminal.

Apple 1


Wikipedia on the Apple 1
Apple 1 Owners Club on AppleFritter
Original Apple owner Joe Torzewski
Digibarn Jef Raskin, manuals, advertisements, photos of an original Apple 1 (note the interview in mp3 sound and video of 2004 with the Woz)
Briel Computers for the Apple 1 Replica and all manuals and information known for the Apple 1
SB-Projects, San Bergmans’ description of the working of the Apple 1 and all about the A-ONE

Datasheets of the now rare Signetics ICs in the Apple 1 (available on every Apple 1 page, but they are all the same documents scanned by me, Hans Otten!)

Apple 1 software

The Apple 1 comes with the WOZ monitor. A very small but smart program, since there is only 256 byte available in the PROM of the original.

It can do just the basic:

1. The prompt is the ‘@’
2. Enter one or two hex numbers, separated by a dot, and it shows you the content of memory from first to last number
3. Enter a hex number to be put in memory, by specifying the address, a ‘:’ and then the hex number for that memory location. Or as many bytes for consecutive locations.
4. Run a program from a memory location.

The monitor is so simple, smart enough to be usable for the replica’s. Via the serial interface you can dump standard hex files to the Apple 1!

The API of the Apple 1 is not much more than:

1. read a character from the keyboard
2. Read a line form the keyboard
3. Write a character on screen
4. Write a hex string to the screen

When the optional cassette interface is added, some more comamnd are added to read and write data from and to an audio cassette tape recorder. Be warned, the Apple 1 cassette interface is very strict about the quality of the tape! With other words, its a disaster to work with.

Apple 1 Basic

Steve Wozniak wrote, by hand, no assembler used, a Basic interpreter for the Apple 1, fitting in 4K. No floating point, a prerunner of Integer Basic for the Apple 1.
Good enough to run simple Basic programs, 4K is not much memory. Mostly text based games. Some are still available.

And that is all what is available for the Apple 1 from the old days!

Krusader and A1 Assembler

Ken Wessen has produced an assembler, disassembler and debugger and even added a small powerful machine monitor . The program is called Krusader and it fits in 4K. Built in in the Apple 1 Replica and the A-ONE.

Visit the Krusader homepage, where also a working version of the Apple 1 emulator POM-1 can be found.

San Bergmans produced also an assembler package for the Apple 1, called A1 Assembler. A small sister or subset of his impressive SB-Assember. More powerful than the Krusader assembler, but no debugger. Can be used on any Apple 1 and is built in in the A-ONE.

Programming languages

Ports of Lee Davison’s excellent 6502 Basic, and Figforth are available. For these you will need the A-ONE or Replica since these have 32K RAM to play with.

Cross assembling/compiling

Any 6502 assembler on another platform that can produce hex files can be used to develop programs on the Apple 1. Dont worry about the Apple 1 API, since there is nearly nothing …

The CC65 package, a C compiler and assembler for the 6502, can also be used with the Apple 1 CC65 patches


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.



  • 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: PS2 Keyboardinterface
  • RS232: 9-pin SubD Female, 2400 Bd
  • Expansion: 2×22 Edge Connector
  • Powersupply: recommended is single universal AC-DC Adapter
  • Voltage: DC 9-12VDC
  • Supply Current: 250 mA
  • PCB Size: 160 x 100mm

A-ONE Extended

The A-ONE Extended is a standard A-One with additional a large breadboard and three Apple 1 slots. Together with the breadboard prototype board this make it quite an impressive system to develop hardware for 6502 systems!




Note the USB connector (on the breadboard side of the board)!

A-ONE extensions

Since the Apple 1 is a standard, it must be possible to use the Apple 1 and Replica 1 extensions, such as the CFFA1 and the multi-I/O board on the A-ONE. No reports on that yet.

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



A-ONE information

The design of the A-One is well documented and open: see the excellent website of San Bergmans

Apple 1 Replica

There are several Apple 1 clones made! The Replica-1 SE by Vince Briel was the first to apply modern components to replace the hard to get and therefore expensive components, like the Signetics 2513 and such, with modern microprocessors emulating the terminal part. The terminal part is replaced by three microcontrollers, for video and serial interface. Before he made the Micro-KIM, Vince Briel designed quite a complex replica of the Apple 1. Complex because of the now defunct, hard to get components. He worked around that problem beautifully with innovative modern solutions and added conventient modern connections like USB and PS/2 keyboard. The result is the Apple 1 Replica (SE). Available are a slot expansion for three real Apple 1 slots, a multi-I/O board with ACIA 6551 and 6522 VIA and, via Rich Dreher, the CFFAA1 (Compactflash mass memory) board.

Some differences between the Replica-1 and the A-ONE.

  • The A-ONE is even more compact, less IC’s.
  • The A-ONE has a real Apple 1 slot instead of the pinheader on the Replica-1.
  • No parallel keyboard interface on the A-ONE, the PS/2 input functions as the keyboard. On the Replica both parallel and PS/2 can be used.
  • Selection of NTSC or PAL on the A-ONE delivers a rock solid picture.
  • The Replica-1 has USB, also functioning as power supply, as an option also as serial interface.
  • The Replica-1 has an AT(X) power connector, required for the -12V of the serial Apple keyboard.
  • The Replica 1 has a EEPROM, the A-ONE an oldfashioned EPROM.
  • The forum of Briel Computers for the Replica-1 gives good support for the community.
  • The Replica 1 is still available for sale, in new variants.

Replica 1 block diagram

The simple block digram. Applicable also to the A-ONE and the original Apple 1. Though only the Replica1 has EEPROM!

Replica 1 block diagram

Video problems

The Replica might have trouble with some video monitors, especially in 50 Hz/Europe countries. Look with a scope at the composite video signal, it is much too low amplitude, a wonder the monitors did sync after all.
The video monitor has a 75 ohm load. In parallel with the 100 ohm R3 this was giving a too low amplitude to let the monitor sync fast enough.

As a dirty hack clip the R3 resistor off and the video becomes stable on many monitors. But not on all!

Replica 1 video