Show HN: Simple Gameboy Emulator

#1

Post by sacert » Fri, Dec 29, 2017, 11:58 PM UTC

Show HN: Simple Gameboy Emulator
github.com

Re: Show HN: Simple Gameboy Emulator

#2

Post by styfle » Sat, Dec 30, 2017, 1:19 AM UTC

I know nothing about emulators, so it would be nice if the README provided instructions for how to build and run the emulator.

Here is some inspiration: https://github.com/dolphin-emu/dolphin

Re: Show HN: Simple Gameboy Emulator

#3

Post by santaclaus » Sat, Dec 30, 2017, 1:25 AM UTC

It would be really cool if someone web-assemblied the best of class game system emulators and exposed them all through a uniform web interface. All vintage game consoles accessible through a single site!

Re: Show HN: Simple Gameboy Emulator

#4

Post by jonny_eh » Sat, Dec 30, 2017, 1:26 AM UTC

santaclaus wrote: post #3

It would be really cool if someone web-assemblied the best of class game system emulators and exposed them all through a uniform web interface. All vintage game consoles accessible through a single site!

https://archive.org/details/consolelivingroom

Re: Show HN: Simple Gameboy Emulator

#5

Post by sacert » Sat, Dec 30, 2017, 1:46 AM UTC

styfle wrote: post #2

I know nothing about emulators, so it would be nice if the README provided instructions for how to build and run the emulator. Here is some inspiration: https://github.com/dolphin-emu/dolphin

You're right, I should've included that from the get-go. Included one now, hope it helps :)

Re: Show HN: Simple Gameboy Emulator

#6

Post by tnecniv » Sat, Dec 30, 2017, 2:28 AM UTC

Making a Gameboy emulator was one of my favorite and most instructive personal projects.

It's worth noting that there was actual extra hardware built into the carts, so you need to implement certain features like extra RAM based on the cart ID in the ROM file.

Re: Show HN: Simple Gameboy Emulator

#7

Post by andrewmcwatters » Sat, Dec 30, 2017, 2:28 AM UTC

I'm impressed! Very clean code. I had no idea a Game Boy emulator could be expressed so simply. Thanks for sharing this, sacert.

Re: Show HN: Simple Gameboy Emulator

#8

Post by rebootthebox » Sat, Dec 30, 2017, 2:34 AM UTC

Great! The CPU.c code is quite instructive since I'm writing a toy VM in my free time. Starring this :)

Re: Show HN: Simple Gameboy Emulator

#9

Post by deaddodo » Sat, Dec 30, 2017, 2:52 AM UTC

tnecniv wrote: post #6

Making a Gameboy emulator was one of my favorite and most instructive personal projects. It's worth noting that there was actual extra hardware built into the carts, so you need to implement certain features like extra RAM based on the cart ID in the ROM file.

Not the cart ID, you're looking in the cart header at byte 0147 for the actual hardware (MBC1, MBC2, MMM01, etc) functionality in conjunction with bytes 0148 (ROM size) and 0149 (RAM size) for specific bank sizing/mapping.

Re: Show HN: Simple Gameboy Emulator

#10

Post by deaddodo » Sat, Dec 30, 2017, 3:01 AM UTC

rebootthebox wrote: post #8

Great! The CPU.c code is quite instructive since I'm writing a toy VM in my free time. Starring this :)

They're using a relatively simple opcode map, but most instructions are logically redundant as can be seen here:

http://www.pastraiser.com/cpu/gameboy/gameboy_opcodes.html

The next step in emudev, with most compiled/systems languages at least, would be to create macros (such as OP_LD or OP_ADD) that generates static instructions at compilation. Another, cleanish method, in C is to generate a 256-length function pointer (void*) based static array and map those generated functions to that, to make the dispatch step simpler. Small trade off, performance-wise, but rarely matters for 8-bit CPU's (where you would usually use an opcode table over an instruction decoder).