Reverse Engineer

I present to you my Apple II+ replica done entirely with jellybean parts and no microcontroller! I chose the II+ over the IIe because it was the last Apple II made from mostly discrete parts, the IIe used a lot of proprietary ASICs.

Some trade-offs had to be made to keep the complexity under control, the original Apple II+ has a fairly large amount of chips, but enough compatibility remains to boot Basic, ProDOS, many games, and even use an original floppy drive or load tapes if you want. Additions have also been made. The CPU is a 16bit 65c816, and there is 128K of memory (only 64K available to Apple II programs).

The project is split in two PCBs (Gerbers and project files at the end):

1. The motherboard consists of the CPU, RAM, ROM, clock, addressing and banking logic, bus expansion, and the audio circuitry (beep and tape). This is enough to boot into Basic through a debugger.
2. The daughterboard contains the logic to generate composite video, the floppy drive controller, the Apple II keyboard decoder, and three extension slots.

At the time it was cost prohibitive to make a single large PCB. But, now that the prices are a lot lower, I would love to combine both boards on a 15cm x 20cm.

The first working prototype

The first prototype was very minimal and had no bank switching or input/output. But through a debugger connected to its extension slot it was able to run Zork and even run some graphics-mode basic code.

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