Reimplementing an Apple ][+ on an FPGA

1977's Apple ][+ was the first successful personal computer, inspiring a generation of hackers and makers and coders; famously, it shipped with a schematic that showed how the boards and their components worked together, to allow hobbyists to improve and service their PCs (hardware-hacking legend Bunnie Huang credits these schematics with igniting his interest in electronics and computing).

In 2007, Columbia University's Stephen A. Edwards decided to reimplement the beloved system using a field-programmable gate array (FPGA), a kind of programmable chip that is much-loved by hardware hackers.

He's published a technical report on the project, along with (appropriately enough) the files needed to reproduce his feat and improve on it.

The Apple II has been documented in great detail. Starting with the first Apple II "Redbook" Reference Manual, Apple itself has published the schematics for the Apple II series. When Woz spoke at Columbia, he mentioned this was intentional: he wanted to share as much technical information as possible to educate the users. Such an attitude is rare these days.

Two third-party books provide even more detailed commentary: Winston Gayler's The Apple II Circuit Description (Sams, 1983), and Jim Sather's Understanding the Apple II (Quality Software, 1983). I consulted both frequently while writing the VHDL for this project. For understanding the Disk II and more precisely, Apple's disk operating system (DOS 3.3), Don Worth and Pieter Lechner's Beneath Apple DOS (Quality Software, 1983) is second to none, although it is much more software-focused than the first two books.

Apple2fpga: Reconstructing an Apple II+ on an FPGA
[Stephen A. Edwards/Columbia University]

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