MUDSTONE

An Atari 2600 emulator with precise beam timing. The 2600 has no frame buffer, so games draw the picture by changing the TIA's registers while the screen is being drawn, and being off by a few colour clocks is enough to ruin the image. Mudstone runs the TIA one colour clock at a time with the 6507 in lockstep, so sprite positioning, HMOVE tricks and mid-line register changes happen exactly where they do on real hardware.

It does this without any per-game fixes. Games that are notoriously hard to emulate now simply work: the starfield in Cosmic Ark, which relies on a quirk of the TIA, looks just as it does on a real console, and the Triplet demo runs flawlessly. Across dozens of commercial and homebrew games, the picture matches Stella, the long-established reference emulator, on every frame.

Cartridges load as .a26 or .bin, with all the common bank-switching schemes: 4K, Atari's F8, F6, F4 and F0, the Superchip variants with extra RAM, CBS, Activision, Parker Brothers, M-Network, Tigervision, CommaVid, SuperBanking and more. The scheme is detected from the ROM and a per-game database, or you can set it yourself. NTSC and PAL cartridges both work, with the region detected from the length of the game's frame. Pitfall II's DPC chip is emulated too, and its music has its own volume control so you can balance it against the sound effects.

The TIA's two sound channels are synthesised band-limited from the same polynomial counters the hardware uses. All the console switches are there: reset, select, both difficulty switches, and colour or black-and-white. Joysticks and paddles are supported, and a paddle can be controlled with an analog stick or with the D-pad at an adjustable speed.

Available on Windows, Linux, macOS, Android, iOS, and WebAssembly. Mudstone is written in plain, portable C11 with no unusual dependencies, so porting it to game consoles is straightforward. Contact us if you are interested.

Retro City Skyline

Mudstone in Action

Unmodified commercial games running on Mudstone.

Adventure running on Mudstone
Adventure © 1980 Atari, Inc.
Pitfall! running on Mudstone
Pitfall! © 1982 Activision
River Raid running on Mudstone
River Raid © 1982 Activision
Yars' Revenge running on Mudstone
Yars' Revenge © 1982 Atari, Inc.

Mudstone Options

Third-Party Software