Cloning the ET-3404 6809 adapter for the Heathkit ET-3400

Dr. Scott Baker made the ET-3404 6809 adapter clone: I’ve become somewhat of a Heathkit ET-3400 enthusiast lately, after building my ETA-3400 memory/io clone. I decided to also clone the ET-3404, which is a 6809 adapter board for the ET-3400. Why? Simply for completeness sake. The official “experiments” for the ET-3404 aren’t all that exciting, […]

Cloning a 6502 Apple-1 in just 930 logic gates

Turning 930 logic gates into a working 6502 Apple-1 clone: Two years ago, the Gigatron arrived on the retrocomputing scene. It needs just 930 logic gates (packed into 33 standard 7400-series ICs) to create a computer that beat ‘complex’ 1980s home computers like the VIC-20 in terms of both CPU power and graphics. Without microprocessor, […]

Yellowstone: Cloning the Apple II Liron

Steve writes: FPGA-based disk control for Apple II is finally working! Six months ago, I began designing a universal disk controller card for the Apple II family. Apple made a bewildering number of different disk controller cards in the 1970s and 80s, and my hope was to replace the IWM chip (Integrated Wozniak Machine) and […]