Skip to content
Custom "Jailbreak" firmware for the Analogue Mega Sg
Branch: master
Clone or download

Mega Sg Jailbreak

Custom "Jailbreak" firmware for the Analogue Mega Sg that allows loading ROMs from the SD Card slot, and an expanded featureset.

Updating Firmware

As shown in this video walkthrough, format a 2GB (or larger) SD card as FAT32 (FAT16 and exFAT are not supported). In Windows, you must use a tool for cards larger than 32GB, such as fat32format.

Place the firmware file msg_firmware_verJB7.4.bin into the root directory of your SD card. Be sure that there is only one firmware file there. Insert the card into your Mega Sg and power on. The firmware will be flashed to the console. This process may take a few minutes.

While the firmware is flashing the LED will turn red and flicker, followed by a considerable pause and HDMI signal blackout. Do not power off. The main menu will boot when it has finished. Delete the firmware file from your card after flashing.

The Mega Sg is protected from bricking as a result of firmware updates, but please still follow the above precautions to be safe.

Organizing ROMs

An empty folder structure is included in MSG JB Drop your ROMs into these subfolders (see SmokeMonster's database for curated lists of ROMs). When loading a core, the Mega Sg will automatically enter the corresponding subfolder. The maximum number of files (ROMs and subfolders) that can be placed in a given folder is around 300-500, depending on the length of the filenames.

Running ROMs

Select browse SD card from the main menu. Hit enter on a filename to run it, or if it's a subfolder, it will enter said folder. The menu hotkey will return to the file menu from the game.


NEVER insert or remove cartridges while your Mega Sg is powered on. Doing so may risk damaging the console and/or losing saves. It is good practice to backup saves before updating firmware.

When a game is exited to the menu, it will prompt you to save. Return to the file menu and save your progress before powering down.


  • JB7.4 2019-04-16

    • includes all fixes from official firmware v4.4:
      • Sega CD - adjusted timing i.e. Mickey Mania
      • Overdrive 2 demo is 100%
      • X-men 2 character select fixed
      • Fixed player 2 XYZ (6 buttons)
      • Allow no controller on player 2
      • SMS fixes for X7 and flash everdrive
      • You now stay in the file browser when selecting a font
      • Changed "hotkeys" to "hotkeys & controllers"
    • plus:
      • Sega CD BIOS substitution works properly now on games like snatcher
      • Fixed speech on Coleco Wizard of Wor
      • Fixed random crashes in Wizard of Wor and majikazo
      • Fixed graphics issue on Juno First and Astrododge
      • Fixed sprites sticking around between games
      • Added warning: CD BIOS replacer only works if fix region is turned on
      • SMS BIOS now also works for cartridges
      • Game gear buffer changed to zero delay by default
    • PDF user guide with documentation
  • JB7.3 2019-04-01 Initial release ❤️

    • includes all fixes from official firmware v4.3
    • PDF user guide with documentation


  • Sega CD Region-Free BIOS are problematic even on real hardware, so it's recommended to use an official SCD firmware from the region of game you wish to boot. Also, you must use a PAL CD BIOS for PAL games and NTSC for NTSC.
  • Clean your Sega CD's edge connector with Deoxit before reporting issues.

Cores Supported

  • Genesis/Megadrive
  • Master System and SG-1000
  • Game Gear
  • ColecoVision

Other Features

  • Sega CD BIOS loading
  • ColecoVision Super Game Module and Super Banking
  • and much more!

Problem Reporting and Community Chat

The custom firmware is not coded by SmokeMonsterPacks or frederic-mahe, but please do report problems here at GitHub for support. Priority will be given to jailbreak-specific problems (using ROMs through the SD card slot rather than through the cartridge slot). Feel free to also submit issues for non-jailbreak related problems. You can join the Classic Gaming Discord to chat or troubleshoot in #analogue-mega-sg

Use at your own discretion. We are not responsible for any damage or data loss caused by custom firmware installation or use.

You can’t perform that action at this time.