xyene / nitrous-emulator

🎮 High-performance Java emulator for Nintendo Gameboy and Gameboy Color hardware.

Nitrous Emulator

Nitrous is a high-performance Gameboy Color emulator aimed at squeezing every last drop of performance out of the Java runtime.

It supports many popular games to a playable extent, including:

• Pokemon Silver/Gold/Crystal
• The Legend of Zelda: Oracle of Ages
• Super Mario Bros. Deluxe

You may download Nitrous from the release tab, or build it yourself from the source.

The code is extensively documented, with excerpts and references to the Pandocs where appropriate, so it can be used as educational material for those interested in learning about Gameboy emulation.

Implemented Features

Below is a (partial) list of Gameboy features Nitrous implements:

• Gameboy / Gameboy Color ROM support
• Support for MBC1, MBC3, and MBC5 memory bank controllers (savefile support)
• Fully accurate instruction emulation; perfect score on the cpu_instrs.gb test
• Noise / PCM / square wave programmable sound generators
• Checksum-based recoloring of original Gameboy games when running as Gameboy Color

Performance and Compatibility

For extra rendering speed, Nitrous bypasses the Java2D API to obtain rendering contexts for the various pipelines Java2D supports simultaneously (e.g., on Windows you can switch whether Nitrous should render using GDI, Direct3D or OpenGL at runtime). Though this allows for higher performance by reducing the abstraction of rendering, it comes at the cost of portability.

Currently, Nitrous has been tested on Windows 8 and 10 using Java 8 and 9, and briefly on Ubuntu 16.04 running Oracle's Java 8 binaries. Your mileage may vary with other setups, though Nitrous does make a reasonable attempt to fall back to well-supported APIs.

nitrous-emulator's Issues

Processs Priority

This emulator is quite sensitive to timing, especially with sound. While playing the music in the background, and performing CPU intensive tasks, the sound is often delayed.

It would be nice to work out some way to invoke SetProcessPriority or the like on the system, somehow. JNI? Poking around sun.* classes?

Hang in Zelda: Oracle of Seasons

Waits for FF4D change, but due to double speed mode not being implemented, fails.

Incorrect implementation of FF26

The incorrect implementation of the sound on/off read-only values prevent Zelda: Oracle of Seasons from loading.

Hang in Pokemon Crystal

The following instructions repeat endlessly:

LD A, $FF41
AND $03
JR Z, -6

This is due to the LCDC Status (FF41) not being implemented correctly.