Simulating The Commodore PET

The Commodore PET is one of those computers that feels like it should come with a time machine, a stack of
spiral-bound manuals, and a polite warning that you may start saying things like “I’ll just type it in from the magazine.”
Released in the late 1970s, the PET (Personal Electronic Transactoryes, that’s a real name) bundled the keyboard,
monitor, and brains into one sturdy all-in-one wedge of optimism. Today, you don’t need a basement full of vintage gear
to enjoy it. You can simulate (more accurately: emulate) a PET on a modern computer and get the best of both eras:
retro charm, modern convenience, and far fewer mysterious capacitors plotting against you.

This guide walks through what “simulating the Commodore PET” actually means, the main emulator choices, how ROMs and
media images fit into the story, and the most common “why is my PET yelling at me?” setup problems. We’ll also dig into
what makes the PET uniqueits ROM-based BASIC, PETSCII graphics, 40/80-column displays, and IEEE-488 peripheralsso the
experience feels authentic instead of like a generic “old computer” cosplay.

What You’re Actually Simulating: The PET’s Personality

A PET isn’t just a 6502 CPU running BASIC. It’s a whole little ecosystem: a ROM-resident operating environment, a screen
editor, distinctive character graphics, specific I/O chips, and peripherals that behave like they’re proudly ignoring the
future. Depending on the model you pick (2001, 3000/4000, 8000 series, SuperPET, etc.), your simulated PET may include:

• MOS 6502 CPU running around 1 MHz (fast enough for BASIC, slow enough for reflection).
• Commodore BASIC in ROM (versions varyBASIC 1.0, 2.0, and later 4.0 show up across PET models).
• Character ROM + PETSCII for blocky, lovable graphics made from text characters.
• 40-column or 80-column display (80 columns feels “business,” 40 columns feels “after-school club”).
• IEEE-488 peripheral bus for disk drives and printersparallel, chunky, and proud of it.
• Optional beeper (a tiny audio footprint that still manages to be emotionally loud).
• Cassette storage in early models (the original “cloud backup,” except the cloud is a shoebox of tapes).

A good PET emulator doesn’t just run 6502 instructions. It recreates the memory map, the ROM routines (“KERNAL” functions),
I/O behavior, keyboard scanning, video timing quirks, and sometimes even the peripheral CPUs inside disk drives. That’s
why emulator choice matters: some aim for friendly usability, others aim for accuracy and hardware breadth.

Emulation vs. Simulation: A Quick Reality Check

People say “simulate” a lot (it’s a great word), but most tools you’ll use are emulators: they run software
designed for the PET by recreating the PET’s hardware behavior in software. Some emulators are more “high-level” (focused
on user experience and compatibility), while others are more “hardware-nerd accurate” (timing, edge cases, and peripherals).

If your goal is to play vintage programs, type BASIC, and load disk images, you want a stable emulator with good UI and media support.
If your goal is to write hardware-twitchy demos, test cycle-sensitive code, or explore obscure PET variants and peripherals, you want
a more accuracy-driven platformeven if it feels like you’re flying a vintage plane with a modern cockpit.

Pick Your PET Time Machine: The Main Emulator Options

Option 1: VICE (xpet / “vice_xpet”) The Friendly Daily Driver

VICE is widely known for Commodore machines, and it includes a PET emulator (commonly referred to as xpet or
vice_xpet, depending on the build). It’s a great starting point because it’s practical:
solid keyboard handling, lots of configuration knobs, and broad support for Commodore-ish media formats.

Best for: most people. Especially if you want to boot quickly, mount images, and get work done (or “work,” where work means typing 10 PRINT statements).

Option 2: MAME The Museum-Grade Hardware Playground

MAME (which also covers computers, not just arcade machines) includes PET systems and tends to be very serious about hardware modeling.
The UI can feel different from classic “computer emulators,” but if you like accuracy, breadth, and a “catalog of everything” approach,
MAME is a powerhouse.

Best for: deeper hardware exploration, model variety, and accuracy-driven experimentsespecially if you enjoy learning a tool that can emulate half a century of computing history.

Option 3: Specialized PET Emulators and Web Options

There are also PET-focused emulators built by hobbyists, plus occasional web-based implementations. These can be fantastic for specific
use-cases (e.g., lightweight testing, educational demos), but they vary widely in accuracy, maintenance, and media support. If your goal
is long-term reliability and broad compatibility, VICE and MAME remain the two safest “big tent” choices.

The ROM Question: The One Part Nobody Mentions in Retro Movies

Emulators generally need ROM images: dumps of the PET’s BASIC ROM, KERNAL ROM, and character generator ROM. These ROMs
are part of the machine’s identity. Switch ROM versions and you may change behavior in subtle (or not subtle) wayseverything from
BASIC commands to screen handling to compatibility with certain programs.

A practical rule: match the ROM set to the PET model you’re emulating. An 80-column PET with BASIC 4.0 isn’t the same
experience as a 2001-era model with BASIC 1.0. If your emulator offers a “ROM set” selector, use it. If it asks you to point to ROM files,
keep them organized by model and version. Your future self will thank you, and your present self will stop angrily swapping files named
something like rom-901447-24.bin at 2 a.m.

Also: be mindful of copyright and legality. Many communities preserve ROMs for historical reasons, but the safest route is dumping ROMs
from hardware you own or using ROM sets distributed in a clearly legal way. (Retro is fun; legal trouble is not fun.)

Media Images: Disks, Tapes, and the PET’s “Files, But Make It 1979” Lifestyle

Once you have ROMs, you’ll want software. PET software typically arrives as:

• Disk images for IEEE-488 drives (different drives use different disk formats/capacities).
• Cassette images (especially for early PET programs and distributions).
• PRG-style program files (depending on the emulator ecosystem and how the software was archived).

Here’s the gotcha that trips up a lot of first-timers: not all “Commodore disk images” are interchangeable.
PET/CBM drives like the 2040/3040/4040 family are not the same as later C64-oriented drives in how they format and handle disks, and
higher-capacity IEEE-488 drives (like the 8050/8250/SFD-1001) have their own formats too. Emulators like VICE know about multiple disk
image types, but you still have to attach the right kind of image to the right kind of drive.

If you attach the wrong image type and nothing works, you didn’t “break the emulator.”
You just tried to feed a PET the wrong flavor of floppy. Vintage computers are picky eaters.

Quick Start: Running a PET in VICE (xpet / vice_xpet)

1) Choose a PET model that matches your goal

Want the “classic” all-in-one vibe? Try an early 2001-style setup (40 columns, cassette culture). Want an “education lab” feel?
A 4032/8032 era machine is a sweet spot. Want “big PET energy”? Explore the 8000 line or the SuperPET angle.

2) Point VICE at the correct ROMs (if needed)

Many VICE builds can auto-detect ROM sets if they’re installed in expected directories. If not, you’ll set ROM paths in the emulator settings.
Make sure BASIC/KERNAL/character ROMs align with the chosen PET model, especially if you’re switching between 40-column and 80-column systems.

3) Fix the keyboard before you blame your life choices

PET keyboard layouts can be quirky compared to modern keyboards. Good emulators provide keymap options so your PC keyboard can behave
like a PET keyboard. If shifted symbols or graphics characters feel “wrong,” check keymap settings. Once it’s right, it feels great
like you’re driving an old car that suddenly stops pulling to the left.

4) Attach a disk or tape image and autostart

VICE supports a range of disk/tape image formats. Typically you can use an “Autostart” option that both attaches the image and attempts to
run the first program (when the software format supports it). If you’re mounting disks, make sure the drive type matches the image type.

For command-line fans, VICE-style emulators often allow launching with an image file as the last argument. The exact command depends on your build,
but the workflow idea is consistent: start the PET emulator, attach media, then load/run.

5) Calibrate speed and video settings for comfort

Some people want “period-correct slow.” Others want “I’d like my BASIC loop to finish before my next birthday.”
Most emulators let you set speed (100% real-time or faster), and adjust CRT/scanline effects. Use taste. PET phosphor green is a vibe,
but you don’t need to recreate eye strain as a historical reenactment.

Quick Start: Running a PET in MAME

MAME can feel different because it’s designed as a unified system for many machines. The upside is strong hardware modeling and a consistent
way to handle media. The workflow is typically:

1. Select a PET system configuration (e.g., a CBM/PET model) and launch it.
2. Use MAME’s UI (or command line) to attach disk/cassette media to the correct device.
3. Control cassette playback when using tape images (yes, you sometimes “press play,” just like 1979 wanted).

Cassette note: you may need conversion tools

MAME supports certain cassette representations directly (often including WAV-style audio images). If your cassette images are in a different
archival format, MAME provides tools (like castool) to convert between formats for use inside MAME.
It’s one extra step, but it makes sense: MAME treats tapes like tapes, not like magical instant files.

Common Problems (and the Fixes That Don’t Require a Soldering Iron)

“It boots, but the screen looks wrong.”

• Cause: wrong character ROM or mismatch between 40/80-column model and ROM set.
• Fix: verify you’re using a ROM set intended for that model; ensure display mode matches the emulated hardware.

“My program loads, but crashes or acts haunted.”

• Cause: ROM version differences (BASIC 1.0 vs 2.0 vs 4.0), timing assumptions, or peripheral expectations.
• Fix: try the ROM set that matches the software’s era; if it expects an 80-column machine, don’t run it on a 40-column setup.

“Disk images won’t read. Everything is sadness.”

• Cause: drive/image mismatch (e.g., using a high-capacity IEEE-488 image with the wrong drive type).
• Fix: attach the right image type to the right drive model; confirm the emulator’s drive configuration.

“The keyboard is cursed.”

• Cause: keymap mismatch or PET-specific symbols/graphics not mapped comfortably to modern keys.
• Fix: switch keymaps; consider a “positional” mapping (keys correspond by location) vs “symbolic” mapping (keys correspond by character).

Doing Something Real: A Tiny PET BASIC Moment

Once you see the PET prompt, the most authentic next step is to type something small and undeniably yours. Try this simple loop:

Is it revolutionary? No. Is it historically accurate? Absolutely. The PET was a “learn by doing” machine, and BASIC was the on-ramp.
From there, you can explore PETSCII art, simple text adventures, and the surprisingly fun challenge of writing programs that respect
memory limits and screen constraintsconstraints that are oddly refreshing in a world where a toaster has more RAM than a 1977 computer lab.

Going Deeper: Why PET Simulation Still Teaches Useful Skills

Learning low-level thinking without losing your mind

PET-era programming encourages a healthy respect for memory maps, I/O, and constraints. Even if you never write 6502 assembly,
you’ll start noticing how programs interact with the machine rather than treating the machine as an invisible cloud.

Cross-development: writing on modern tools, running on a PET

You don’t have to write everything on the PET. Many people cross-develop: write code on a modern editor, assemble/compile it,
then run it in the emulator. Toolchains like cc65 include PET targets and documentation about PET-specific memory layouts and runtime details,
which makes structured projects more approachable than pure “type hex into a monitor” heroics.

Preservation and experimentation

Emulation keeps old software runnable and helps preserve history. It also gives you a safe playground: you can test software that expects
a particular drive, a particular ROM, or a particular screen modewithout hunting down rare hardware and praying it survives shipping.

Hands-On Experiences: What It Feels Like to Live in PET-Land (About )

The first time you boot a simulated PET, you’ll probably laughpartly because it’s charming, partly because it’s so unapologetically
not modern. The PET doesn’t greet you with icons or a helpful wizard. It basically hands you a prompt and says,
“Okay, you’re the wizard. Go on then.” And weirdly, that feels great.

There’s a particular satisfaction in watching a ROM-based machine come to life instantly. No updates. No login. No “we’ve improved
your experience” pop-up that somehow makes everything worse. Just the PET’s world, ready in a blink. The next sensation is tactile
even though you’re on a modern keyboard: you start thinking in keystrokes that matter. Every character you type has a job.
Even mistakes feel instructive because you can’t hide behind infinite layers of undo and auto-correct. (You can still delete, of course.
But the PET vibe encourages you to pay attention.)

Then you meet PETSCIIthe PET’s lovable character graphics language. If you’ve only known emojis and full-color fonts, PETSCII is like
discovering cave paintings that also happen to be functional UI elements. You can “draw” borders, make little spaceships, or build a
crude dashboard out of block characters. It’s the kind of creativity that happens when the tool is limited but the imagination isn’t.
You’ll find yourself designing screens the way early programmers did: not by importing an image, but by composing one character at a time,
like a mosaic made of letters and squares.

Loading software is where the nostalgia (and the comedy) really hits. Disk images feel almost modernattach, load, run. Cassette images,
on the other hand, are a reminder that storage used to be a process, not a background detail. Even in emulation, tapes can demand
that you manage playback, wait for tones, and accept that “fast loading” once meant “only a little slow.” It sounds inconvenient,
but it changes your relationship with software. You value what you load. You don’t casually open ten programs “just to check something.”
You commit.

The most surprising experience is how quickly the PET becomes a creative writing machine. Not in the modern “open a word processor” way,
but in the sense that BASIC invites you to narrate your intentions line by line. You write a tiny loop. You print a message. You add a
counter. You make it react. Minutes later, you’ve built a little living thing that only exists because you described it precisely.
It’s programming in its most direct, most human form.

And once you start exploring different PET models in your emulatorswitching between 40-column and 80-column systems, trying different
BASIC revisions, attaching different drive typesyou realize “the Commodore PET” isn’t one experience. It’s a family of experiences.
That’s the real joy of simulating it today: you can tour decades of design decisions in an afternoon, compare behaviors side by side,
and understand why old-school developers became such careful thinkers. The PET doesn’t just run programs. It teaches you how computers
used to beand why some of that mindset still matters.

Conclusion

Simulating the Commodore PET is part retro fun, part practical education, and part “wow, we really used to do it like this.”
Whether you choose VICE for an easy, configurable PET daily driver or MAME for museum-grade hardware exploration, the key ingredients are
the same: correct ROMs, correctly matched media images, and a willingness to enjoy the PET’s wonderfully opinionated way of computing.
Start simpleboot, type, run a loopthen expand into PETSCII art, disk systems, and cross-development. You’ll end up with a genuine feel
for early personal computing… and maybe a new appreciation for the humble semicolon.