WIP disassembly of the OS for the Acorn Electron. The following Acorn versions are covered:

• OS 1.00 - ROM supplied with Electron

The following non-Acorn versions are covered:

• OS 3.00 - ROM supplied with Slogger's Master RAM Board

The following unreleased non-Acorn versions from Slogger's old stock are also covered:

• 213-OS-3.00-alt1
• 249-OS-3.00-alt2 - identical to OS 3.00
• 524-OS-3.00-alt4

(There is also an alt3 ROM, but it looks invalid.)

This project is a work in progress. You'll find many holes, many missing comments, and some rather unhelpful label names. The initial goal is simply to separate code and data and ensure everything in the ROM that needs a label has one.

Starting point was JGH's disassembly of the Electron MOS 1.00 here: https://mdfs.net/Info/Comp/Acorn/Source/MOS.htm - this has supplied nearly all the current comments.

This repo has submodules. Clone it with --recursive:

git clone --recursive https://github.com/tom-seddon/mos320

Alternatively, if you already cloned it non-recursively, you can do the following from inside the working copy:

git submodule init
git submodule update

Mandatory:

• Python 3.x

On Unix:

• 64tass (I use r3120)
• GNU Make

(Prebuilt Windows EXEs for 64tass and make are included in the repo.)

Type make from the root of the working copy.

The build process is supposed to be silent when there are no errors and when the output matches the original ROMs. Some versions of make might print a load of stuff about entering and leaving the directory.

The build output is assembler listing files that you can use for reference. Acorn versions:

• build/elk100.lst - OS 1.00

Non-Acorn versions:

• build/os300.lst - OS 3.00