Sometimes you just need to get out the soldering iron and build something. Fortunately I had an Altairduino kit waiting to be built. Nice kit and easy to follow instructions. Couple of small changes to the build instructions. In order to get a nice fitting front panel I chose not to install the top panel first. To do this I held the nuts required to secure the front panel in with tape (see image).

Bus Connector

Yacc1 will be a multi-board system requiring a motherboard, really more of a basic bus-board, for cards to plug into. For my previous 1802 projects single row breakaway headers with a simple bus-board made of either Veroboard or a simple PCB had all the pins, a grand total of 3X, required.




This custom cpu project will require far more interconnects so I ended up selecting DIN 41612 3 x 32 connectors. They physically strong and will withstand the repeated insertions and removals while at the same time quite cost effective


Custom CPU Projects

Misery loves company.

A partial list of custom CPU projects, specifically interested in TTL based projects. Omitted are projects using relays, transistors only, and FPGAs.


Magic 1 


Mark 1 Forth Computer

Mark 2 Forth Computer

A Minimal TTL Processor for Architecture Exploration

Time Fracture D16/M

Technical Article Folder

Galactic Electronics 4 bit machine

Apollo 181


8 bit ttl cpu

nibbler 4


Kino 74

Project Space 8 bit ttl CPU

4 bit scratch built CPU



1802 World

1802 World

* System-5 for Running ELF/OS *

Click the image to take a look

My first brush with the 1802 was late 1977, like so many others the series of articles in Popular Electronics got me hooked. My first project was on a solderlss breadboard I wired 0x7B onto the data bus by directly connecting D0 through D7 to the appropriate +5V and GND signals and connected an LED and resistor to the Q signal. Using wires connected to the control lines I reset the CPU and then set it to run. I pulsed the clock line with a de-bounced switch and after 21 pulses the LED connected to the Q line lit up. From that moment on I was hooked. Comments to Ken

Front Panel from System-1, every real computer has a front panel.


Srecord-1.20 is a very useful tool for manipulating various ASCII/HEX/BINARY files for creating EPROM images check for the latest information.

Source: srecord-1.20.tar.gz

Documentation: srecord-1.20.pdf

Source: srecord-1.23.tar.gz

Documentation: srecord-1.23.pdf

RCASM is the assembler needed by several of the Makefiles to build the BIOS
Source Zip File: rcasm.tgz

Board Construction Notes

Last Updated Mar. 08/2005

Board size 5.50 x 3.75

Bus Connector placement

Center location 0.2 x 1.875 (set Eagle grid to 0.025 to place connector and then restore to 0.05)

Restricted areas

Layer 41 and 42 place 3.00 x 0.15 polygons left and right bottom corners (next to bus connector) to prevent

traces from contacting card supports

LED Placement

Cathode (flat section) facing inward toward bus connector

5.2 (X axis) by

(y -axis)

0.3 Power – Label PWR 5.4 x .45

1.0 Aux 1 – Label xxx 5.4 x xxx

1.7 Aux 2

2.4 Aux 3

3.1 Aux 4

Eagle Library components

LED type 5MM

Resistors 207/7

Bypass capacitors C025-050×050

Tantalum capacitor placement .45 x 3.45 (+) closer to VCC

Board Labeling

NAME Label .05 x .05


XXX = Board name

# = board design (different types of similar function)

A = Revision level

All slik screen writing on layer 25

PC Board Silk Screen uses layers 20, 21, 25

Verify Process

Do ERC Check

Verify GND and VCC Connected at bus

Verify unconnected input pins on pin list

Build Process


Run Script


!!!Update file names and order number inside readme file before uploading zip file for production!!!