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 MegaDisk Interceptor Ultimate Tool
 Build and write Sega Mega Drive floppy disks for the Mega Disk Interceptor
 Developed by Sebbeug (2026)
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WHAT IT DOES
------------
This tool turns Mega Drive ROMs into floppy disk images for the Mega Disk
Interceptor (a floppy-based copier for the Sega Mega Drive / Genesis) and writes
them to real 3.5" disks using a Greaseweazle USB device.

It can:
  - Put a single game on a disk (it boots automatically).
  - Put several games on one disk (a menu lets you pick which one to run).
  - Split a large game (up to 2 MB) across two disks.
  - Create system disks (5.5C for the Specify Card, 4.9B for cartridge dumps).
  - Open an existing .img disk image and write it as-is.


WHAT YOU NEED
-------------
  - A Greaseweazle USB device with a 3.5" floppy drive connected to it.
  - Blank 3.5" HD floppy disks.
  - A Mega Disk Interceptor connected to your Mega Drive.
  - The "tools_gw" folder must sit next to this program's .exe. It contains the
    Greaseweazle host tool (gw.exe) and the megadisk.diskdef definition. If this
    folder is missing, the program will tell you it cannot find gw.exe.


THE GREASEWEAZLE STATUS
-----------------------
The status bar at the bottom shows whether a Greaseweazle is connected and on
which COM port. It updates automatically when you plug or unplug the device, so
you do not have to restart the program.


ADDING GAMES
------------
  - Click "Browse...", or drag and drop files onto the list.
  - Accepted formats: .md, .bin (raw Mega Drive ROMs) and .smd.
  - Drag rows up and down to change the menu order.
  - Double-click a row to rename how the game appears in the on-disk menu
    (13 characters max, A-Z and 0-9).
  - Press Delete to remove the selected game(s).


WRITING A DISK
--------------
When games are in the list, a "Write Disk" button appears. Click it and choose:
  - Yes    = write straight to a floppy (no file is left on your hard drive).
  - No     = save an .img file instead (for later use).
  - Cancel = do nothing.

For a two-disk game, the program writes disk 1, then asks you to insert disk 2
and writes it. On the console: launch the game from disk 1; when it asks for
"INSERT DISK 2", swap the floppy and press C.


WRITING AN EXISTING IMAGE
-------------------------
Use "Tools > Open Image to write" to load a .img file. The list shows its
contents in read-only mode and a "Write Image" button appears so you can write
that image to a floppy unchanged.


SYSTEM DISKS (Tools menu)
-------------------------
  - "Create system disk 5.5C (Specify Card / SRAM)"
        A system disk used with the Specify Card to save and restore cartridge
        SRAM (battery saves).

  - "Create cartridge dump disk (4.9B)"
        A system disk used to dump a physical cartridge to floppy. On the
        console: follow procedure, then press button B (or C).

Both system disks show "NO PROGRAM" when booted - this is normal, they carry no
game, only the loader the console needs.


OPTIONS
-------
  - Verify after write : re-reads the disk to check it after writing. Off by
        default. Note: verification can report errors on track 0 even when the
        disk is actually fine and boots correctly.
  - Pre-erase disk : erases the disk before writing. On by default; improves
        reliability on reused floppies.
  - Drive : which floppy drive the Greaseweazle uses (A or B). Leave on A unless
        your drive is wired as B.

These settings are remembered between sessions.


ABOUT THE DISK FORMAT
---------------------
The images this tool produces are raw 1,595,392-byte disk images. They use a
geometry specific to the Mega Disk Interceptor, so they are not regular PC
floppies and must always be written with the included megadisk.diskdef. The
game data is stored in SMD-encoded form, and a small "INTERCEPT" boot sector is
written so the console accepts the disk.


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