The emulator
An ACE you already own. Same ROM, same BASIC, same everything — it just runs on your laptop instead of your desk.
Use it to try the machine before you build one, to work on a program when the real one's in another room, or to test something without hunting for a CompactFlash card.
In the browser
https://acwright.github.io/6502-EMULATOR/
Nothing to install. Open it, and you get the splash and the OK prompt in a tab. Everything in this guide works there.
On your desktop
There's a proper application for macOS, Windows and Linux, and it's the better option if you're going to use it much: it can attach a CompactFlash image, connect to a real serial port, keep a debug server running, and remember your settings.
Grab it from the 6502-EMULATOR releases page.
The toolbar
Everything happens from the row of buttons across the top:
| Button | What it does |
|---|---|
| CPU chip | Load a ROM, in place of the built-in BIOS |
| Document+ | Load a cartridge |
| Document$ | Load a program (.prg / .bas) into memory |
| ▶ / ■ | Run or stop the machine |
| ↺ | Reset — exactly like the button on a real ACE. Memory survives. |
| ⏻ | Power cycle — the cold start. Memory is cleared. |
| 1 MHz / 2 MHz | Switch CPU speed |
| Clipboard | Paste text in as keystrokes |
| ⚙ | Settings |
Settings has the same file rows, plus what's currently loaded and an ✕ to unload it again.
Pasting a program in
Ordinary ⌘V / Ctrl+V won't work, because the emulator sends every keystroke straight to the machine. Use the Clipboard button instead: paste your listing into the box it opens, and the emulator types it in for you. It's the quickest way to try anything longer than a couple of lines.
Attaching a card
Settings → CF Card. In the desktop app, Select… picks a .img file — the sort cffs builds — and it stays attached across restarts. In the browser, Load uploads one and Export downloads the current card so you can keep it.
Once it's attached, DIR, LOAD and SAVE work exactly as they do on hardware, and what you save is written back to the image. The ✕ goes back to the emulator's own blank card.
The NVRAM row works the same way, for the 256 battery-backed bytes.
Talking to real hardware
The desktop app can open one of your computer's serial ports. Pick the port, set it to 19200 8-N-1, connect — and now the emulated ACE is on the other end of a real serial cable. Which means you can use it as the terminal for a real ACE, or move files between the two with XModem. See Serial and a terminal.
Fullscreen
F11, or ⌘+Return on a Mac. The picture keeps its 4:3 shape whatever the window is doing.
Running it from the command line
The desktop app installs a 6502 command (Settings → Command Line → Install). It's how you'd fold the emulator into a build:
6502 run --headless mygame.prg--headless runs with no window at all, wired to your terminal. Useful flags:
| Flag | What it does |
|---|---|
--cf disk.img | Attach a card image |
--console video | Use the video screen instead of the serial console |
--freq 2 | Run the CPU at 2 MHz |
--timeout 30s | Stop after a while, whatever happens |
There's a debugger in there too — breakpoints, single-stepping, memory watching, screenshots — which the assembly chapters of this guide use heavily.