Game Boy and Game Boy Color for MEGA65

Play Game Boy and Game Boy Color games on your MEGA65!

Learn more about where to download and how to get started.

This core is based on the MiSTer Game Boy core which itself is based on the MiST Game Boy core.

sy2002 and MJoergen ported the core to the MEGA65 in 2021.

Special thanks to Robert Peip for his invaluable support and to Till Harbaum for creating the original MiST Game Boy core back in the days.

The core uses QNICE-FPGA for loading the Game Boy's BIOS as well as for the on-screen-menu and for loading game roms.

Features

• Game Boy and Game Boy Color support
• Convenient game cartridge browser which supports long filenames
• Joystick support including special mappings so that you can for example play Super Mario Land via joystick
• Optional color grading to desaturate the colors, similarly to how they looked on the LCD display of the original Game Boy Color hardware.
• Support for both MEGA65 SD card slots
• HDMI video and audio (720p @ 60 Hz, on R3 machines only) and in parallel 1280x720 @ 60Hz over VGA and audio via 3.5mm audio jack (on all machines)

Installation

1. Download the ZIP file that contains the bitstream and the core file and unpack it.
2. Choose the right subfolder depending on the type of your MEGA65: R2 or R3
3. Either use MEGA65's bitstream utility (m65 -q yourbitstream.bit) or install the core file so that you can use MEGA65's No Scroll boot menu to load the core. Please have a look at the MEGA65 Starter Guide to learn more.
4. The core needs a FAT32 formatted SD card to load game cartridges (ROMs).
5. If you put your ROMs into a folder called /gbc, then the core will display this folder on startup.
6. The core includes an Open Source Game Boy BIOS. For more authenticity, go to https://gbdev.gg8.se/files/roms/bootroms/ and and download cgb_boot.bin. Rename the file to cgb_bios.bin and place it in the /gbc folder.

Constraints of the current Beta version 0.8

• MEGA65 R2 machines: Maximum cartridge size: 256kB
• MEGA65 R3 machines: Maximum cartridge size: 1MB
• Flickering in rare situations due to no frame blending
• No savegames

Getting started

After you start the core, you see the help menu that explains you how to use the core. Here are the most important hints:

• Choose a Game Boy ROM (normally having the file extension .gb) or a Game Boy Color ROM (.gbc) from any folder of your SD card using the cursor keys and Return to navigate.

• Use Space as the Game Boy's "Start" key and Return as the Game Boy's "Select" key. Left Shift is Game Boy's "A" and Mega 65 is Game Boy's "B". The cursor keys of the MEGA65 are the Game Boy's joypad.

• Only works while a game is running: Press Help to open and to close the Options Menu, where you can switch between Game Boy Classic and Game Boy Color, configure the joystick mapping and choose if you prefer fully saturated colors or colors that are closer to the original Game Boy Color's hardware (color modes).

Some demo pictures

MEGA65 Core Selection	Game Boy Core: Start	Game Boy Core: File Browser
Game Boy Color Boot Screen	Super Mario Start Screen	Super Mario Gameplay Screen

Clarification: These screenshots are just for illustration purposes. This repository does not contain any copyrighted ROMs such as BIOS ROMs or game ROMs.

Joystick usage and mapping

Basic usage: Just plug-in your joystick in port #1 or #2 of the MEGA65. Both ports are working. By default the fire button of the joystick is mapped to the Game Boy's A button, which should be fine for many games.

Certain games such as Castlevania and Super Mario Land are using the A button to jump. When using a joystick, you would expect that moving the joystick up would mean jumping. For this kind of games, this core supports a feature to change the joystick's mapping. Press the Help key while the game is running and choose Up=A, Fire=B as shown on the following example screenshot.

The setting Up=A, Fire=B works perfectly for Super Mario Land and Castlevania and all other games that are having this "A to jump, B to fire" kind of logic: When you move the joystick up, the "A" button is transmitted. In parallel also the press of the GameBoy joypad's "up" direction is transmitted in this case, so that in a game like Castlevania you can jump when you move the joystick upwards as well as climb upwards. The joystick movements are feeling as natural as you would expect it.

Color modes

The Game Boy Color’s screen was surprisingly good for its time. Yet, it was not able to reproduce the colors as accurately as any modern screen and the result was a slight bit of washing out of the colors. The game developers were aware of this phenomenon of course and chose their color palettes accordingly.

This is why some games might look too colorful, too saturated or simply strange when running on this core today. There is no specific pattern and no rule when this happens. And it also has something todo with personal taste and preferences.

You can choose between two color modes using the Help menu while the game is running: "Fully Saturated" shows the raw colors and "LCD Emulation" performs a color grading to approximate the historical color LCD screen. Have a look at the following example screenshots from the game "Adventures of Elmo in Grouchland" to see the difference:

Fully Saturated	LCD Emulation

You can see how the rather bright yellow color of the house and the pavement turns into an orange/brown tone and how Elmo himself turns from a clear red into a ruby color. Also the sky, the tree and the fence are adjusted.

SD Cards

SD cards need to be formatted with FAT32. If you have a folder called /gbc, then the file browser will switch to this folder by default.

Both SD card slots of the MEGA65 are supported. The back slot ("external") has precedence over the bottom tray slot ("internal"). That means:

• If during startup/reset an SD card is inserted into the external slot, then this SD card will be chosen.
• If, while the file browser is open and the internal slot is active, an SD card is inserted into the external slot, then the file browser switches to the external slot. If the card is removed from the external slot, the file browser switches back to the internal slot.

Use F1 to switch to the internal card while the file browser is open and use F3 to switch to the external card.