MUDSTONE

An Atari 2600 emulator built around the one thing the machine cannot be emulated without: the beam. The 2600 has no frame buffer, so every game draws by changing the TIA's registers between one scanline and the next, and a few dozen colour clocks either way is the difference between a picture and a mess. Mudstone steps the TIA at the colour clock and the 6507 in lockstep with it, through the same delayed-write pipeline the real chip has, so the sprite positioning, the HMOVE tricks and the mid-line register changes that define the platform land where they land on hardware.

Cartridges load as .a26 or .bin across the full range of schemes the platform accumulated: 4K and the Atari F8, F6, F4 and F0 banking, the Superchip variants that add RAM, CBS, Activision, Parker Brothers, M-Network, Tigervision, CommaVid, and the rest. Each is recognised per title from a database rather than guessed. Pitfall II brings its DPC chip with it, and its music is mixed alongside the TIA's two channels with a volume control of its own, so the score can be balanced against the effects.

Both the TIA's sound channels are synthesised band-limited from the polynomial counters the hardware uses. The console's own switches are all present: reset, select, the two difficulty switches, and colour or black-and-white. Joysticks and paddles are supported, and a paddle can be driven from an analog stick or emulated from the D-pad with a configurable sweep time.

Available on Windows, Linux, macOS, Android, iOS, and WebAssembly. Mudstone is plain, portable C11 with no exotic dependencies, so a port to video game consoles is well within reach. Contact us if that is of interest.

Retro City Skyline

Mudstone in Action

Commercial games running unmodified on Mudstone, shown to demonstrate compatibility.

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