Virtual Jaguar libretro

Port of the Virtual Jaguar Atari Jaguar emulator to the libretro API.

Features

• Emulates the Atari Jaguar's four processors: Motorola 68000, GPU, DSP, and Object Processor
• Supports NTSC and PAL video modes
• 2-player input with configurable numpad mapping
• Fast and legacy blitter modes (the legacy/accurate path is SIMD-accelerated on SSE2 and NEON)
• Optional BIOS boot sequence, plus an HLE BIOS so games can boot without a BIOS image
• Save state, run-ahead (deterministic serialization), SRAM/EEPROM via the libretro SRAM interface, cheat codes, and a memory map for RetroAchievements
• Supported ROM formats: .j64, .abs, .jag, .rom (including inside ZIP archives), plus conservative headerless raw homebrew loading

Recent improvements (libretro fork)

This fork has diverged substantially from upstream Virtual Jaguar v2.1.0. See docs/WHATSNEW for the full v2.2.0 changelog. Highlights:

• HLE BIOS now produces hardware-equivalent post-boot state — MEMCON1, clocks, GPU auth magic, OLP, exception vectors, TOM/JERRY timing — and the vast majority of commercial titles boot cleanly without any BIOS image. 200+ pin tests in test_hle_bios cover the contract.
• Game-specific fixes: Alien vs Predator red noise (M2 blitter BKGWREN+BCOMPEN), Doom resolution (proper PWIDTH pixel replication, replaces the legacy hack), and audio dropouts at frame edges across many titles (interleaved JERRY events). Jaguar CD support is in flight on a separate branch (PR forthcoming).
• CPU accuracy: DSP 40-bit MAC accumulator semantics, FLAGS-write dispatch, GPU/DSP IMASK preservation and ADDC carry overflow, DIVL exception PC.
• Accurate-blitter accuracy fixes (daddmode NAND tree, daddbsel bit 3, ADDARRAY cinsel carry, SRCSHADE color).
• Object Processor: scaled and fixed-bitmap firstPix handling, left/right/reflected edge clipping for scaled bitmaps, firstPix for 2/4/16/24 BPP fixed bitmaps.
• TOM IRQs: pending status now latches even when CPU enables are clear; IPL2 reasserts on enable via the unified TOMAssertEnabledIRQs path. Selective clear works correctly when multiple sources are pending.
• Headless test surface: make test runs HLE-BIOS pin tests, event queue tests, blitter SIMD bit-exactness, DSP MAC40 semantics, save-state round-trip / rewind, cheat decoders, libretro memory-map / RetroAchievements wiring, plus a screenshot regression diff via miniretro on push.
• Performance: ~2x speedup on DSP/GPU/memory hot paths, audio refactored to drop per-sample events.

Building

make -j$(getconf _NPROCESSORS_ONLN)            # Auto-detects platform
make -j$(getconf _NPROCESSORS_ONLN) DEBUG=1    # Debug build
make platform=ios-arm64                         # Cross-compile (ios-arm64, osx, unix, win, android, switch, vita, etc.)

Output varies by platform: .so (Linux), .dylib (macOS), .dll (Windows).

Documentation

• File format details
• Source layout
• Changelog
• Known issues & TODO
• Security policy & binary verification
• libretro documentation

Links

• Upstream: git clone http://shamusworld.gotdns.org/git/virtualjaguar
• Unofficial GitHub mirror: https://github.com/mirror/virtualjaguar

Contributors

This project is built on the work of many contributors. See the full list on GitHub.

• Original Virtual Jaguar by David Raingeard (Potato Emulation).
• SDL/Linux/Win32 port by Niels Wagenaar & Carwin Jones (SDLEMU).
• Cleanups, GUI/Qt port, and ongoing upstream maintenance by James Hammons (Shamus).
• libretro core port by libretro/RetroArch contributors.
• libretro fork maintenance — Joseph Mattiello (@JoeMatt).

License

Licensed under the GNU General Public License v3.0.