Chihaya (千早)

“If I can be the best in the world at something, then I think it's worth a shot.” - Chihaya Ayase

Chihayafuru, by Yuki Suetsugu

A CHIP-8 emulator written in Clojure.

Progress

• CPU
• Display
• Input
• Sound
• Timers

Known issues:

• Sound timer is implemented but the buzzer doesn't work.
• CPU is missing the following instructions:
  • SUBN Vx, Vy
  • JP V0, addr
  • LD Vx, K

Building

Prerequisites

• JDK 8
• Clojure
• Chip-8 font: follow instructions here.

Compiling

$ clj -Auberjar
[uberdeps] Packaged target/chihaya-0.1.0.jar in 2786 ms

Running

Pong: (SHA1: a60611339661e3ab2d8af024ad1da5880a6f8665)

$ java -cp target/chihaya-0.1.0.jar clojure.main -m com.unsafepointer.chihaya.core
Usage: chihaya [OPTION] ... <romfile>
  -i, --instructions         Output instructions to stdout
  -f, --frequency FREQ  800  CPU clock rate
  -h, --help

CPU frequency

Chip-8 has no formally defined processor speed at all. Chihaya renderer is locked at 60 Hz, running whatever number of instructions have been defined using the --frequency flag, which defaults to 800 Hz. Most games do best when you are running around 400-800Hz, but you have to check documentation per game.

CPU Tests

corax89/chip8-test-rom: test_opcode.ch8 (SHA1: f1cfcffe1937ed6dd6eeed1a7f85dfc777bda700)

Acknowledgments

This emulator, like many others, is based on the Cowgod's Chip-8 Technical Reference v1.0. For ease of access and review purposes, relevant parts of the specification are pasted before the implementation.