ARB PocketBeagle Emulator

This project consists of replacing the motherboard of one of the most beautiful chess computers, the Chafitz (Applied Concepts) ARB Sargon 2.5 by AVE Micro Systems, with a new one with the following assumptions:

  • No need for cartridges, all programs embedded on the motherboard.

  • Keep compatibility of I/O circuits.

  • Do not distort the Real-Time Control.

  • Raise the computing speed as much as possible.


One of the most pleasant and nice things about this project is that several people have been involved:

  • Wolfgang Zugrav is the heart and soul of the project: he conceived the idea, took care of the leadership and coordination between the different participants, provided financial support to the whole project...

  • Heinrich Hawig is responsible for the development of 6502 emulation software and the initial electronic design.

  • Johannes Seif did all the analysis of the original code, and programmed the necessary modifications to roms 2.5, 3.0 and 3.5 to make them equivalent to 4.0. A huge effort, considering that these are modifications such as: speed adoption to make LEDs and beeper work properly; implementing "hint" / "display move" (DM); implementing "show depth"; etc.

  • I took care of making the final electronic schematics, PCB layout and manufacturing, assembly of all the motherboards, initial testing, etc.

  • Johann Feischhacker is now in charge of a not easy job, the restoration and conditioning of all the ARB chessboards, performing a craftsmanship work with a quality that is beyond the original.


Let's look at this project in detail...

ARB (Auto Response Board) Sargon 2.5

View of cartridge inserted

Cartridge with Sargon 2.5 program

Original motherboard (It doesn't have any ROM)

Specifications of the original computer:

  • Microprocessor: 6502 (8-Bit)

  • System Clock: 2 MHz

  • RAM: 2 KB

  • ROM: 8 KB (Sargon 2.5 version)

  • Approx. ELO: 1400

For the emulation of the 6502, a BeagleBone minicomputer is chosen.

These boards are low-cost, fan-less single-board computers based on low-power Texas Instruments processors featuring the ARM Cortex-A series core. The particular model chosen is the PocketBeagle:

PocketBeagle Rev A2

  • Based on Octavo Systems OSD3358-SM 21mm x 21mm system-in-package that includes 512MB DDR3 RAM, 1-GHz ARM Cortex-A8 CPU, 2x 200-MHz PRUs, ARM Cortex-M3, 3D accelerator, power/battery management and EEPROM.

  • 72 expansion pin headers with power and battery I/Os, high-speed USB, 8 analog inputs, 44 digital I/Os and numerous digital interface peripherals.

  • MicroUSB host/client and microSD connectors.

Thanks to Heinrich's work, the PocketBeagle emulates the 6502 at an equivalent frequency of approximately 130 MHz.

It includes not only Sargon 2.5 but all other versions: 3.0, 3.5 and 4.0. And also the checkers game "Avelan"!

The motherboard incorporates a connection of an external emulator, for future development. And it is assembled in two different versions: one with AC power input (compatible with the original ARB transformer), and another version with DC power input (more energy-efficient and more versatile).

ARB PocketBeagle Emulator
Power input = AC 9 V

ARB PocketBeagle Emulator
Power input = DC 7.5 to 12 V

First testing:

Initial performance tests, running Sargon 4.0, have reported more than 2100 ELO.

First batch

Second batch

This project is still under development.

Below we can see the chessboards, restored by master craftsman Johann Feischhacker, which will contain the new motherboards: