FIELD NOTES / RECURSE CENTER
Merlin Pro on the
Recurse Center Apple IIe
The goal: program in assembly directly on the Apple IIe. A popular program for just this purpose is Merlin Pro.
About the RC Apple IIe
The Apple IIe at Recurse Center is… an Apple IIe. Not to be confused with the Apple II or the Apple IIc. Ours has a whopping 128 KB of RAM, built-in Applesoft BASIC, and two floppy disk drives.
Hardware breakdown
On the desk: the Apple IIe, a Commodore 1702 monitor, and a writable Maxell MD2-D floppy disk. There are two AUX cables, one with a USB-C-to-aux adapter. They’re labeled audio in and audio out; audio in goes into the Apple IIe.
Those audio jacks were originally for cassette tapes. We’re using the audio input to get Merlin onto the machine, with a laptop playing the part of the cassette player.
Actually, let’s see computer go brrr ↗
Getting Merlin onto the Apple
The project contains the original ProDOS Merlin Pro 2.33 disk images, A and B. To get Merlin onto the physical machine, we use c2t—“code to tape”—to turn a disk image into audio, then send it through the Apple’s cassette input.
The practical details live in the transfer notes: the connection, the successful audio transfer, and the plan for backing up floppies. For the setup experiments and hardware identification, see the session notes.
Project contents
disks/- Original ProDOS Merlin Pro 2.33 disk images A and B.
audio/- Audio files for sending Merlin through the Apple’s cassette input.
tools/c2t-src/- The code-to-tape converter source.
SHA256SUMS- Checksums for the disk images, audio, converter, and source.
Now for the assembly
Merlin gives us an editor and an assembler on the Apple itself. The Merlin notes cover display controls, editing, assembly, saving, and loading.
You can also jump straight into machine code through the Apple’s built-in monitor. That’s what the browser experiment does: enter 26 bytes, run them, and change a single byte to see what happens to the screen.
References
Adapted from README-human.md. These are working notes from a real machine, with more to figure out.