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How to create a .GDI GD-ROM image for SEGA Dreamcast console

Dreamcast's profile picture
Published in 
 · 9 Apr 2022

It turns out that creating a complete GD-ROM image (.GDI file) is not as trivial as it may seem. Unfortunately, there is no simple tool to create a complete file with all structure and paths.

It took me some time to create the guide for you, but I finally made it!

The following guide will definitely be useful to everyone who uses Dreamcast emulators, owners of a virtual drive like GDEMU / USB-GD-ROM, translators and other romhackers or mod makers.

Let's go to work.

We need:

  • any GDI image
  • GD-ROM Explorer by jc
  • GDIbuilder program
  • optional GDIUtlis program

First, we need to obtain a full copy of the required GD-ROM.
For example, by copying it yourself using the DCSD Riper or by downloading it from various websites.

After exporting the required files, e.g. using GD Expoler, you can perform the necessary work. Important! You must keep the disc.gdi file and the Audio tracks in .RAW and .BIN format, except for track3.bin - we will create the largest track (about ~ 1.2GB) by ourselves.

GD-ROM tracks Dreamcast
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GD-ROM tracks Dreamcast

A little note! If you come across an image that GDExplorer is unable to open, you must repair its structure.

Don't ask why, somebody complicates their lives (as is the case with whole REDUMP sets that are senselessly written in ISO, which are not supported by anything). It is incomprehensible to me. We will use the GDIUtlis program to repair the file of such a file. We choose the path with the unreadable GDI file (Input GDI file) and indicate the destination (Output GDI Directory). We need min. 3GB of space for this operation, and then press START . The process will take a while - be patient.

After the conversion is complete, GDROM Exploler will be able to read the entire repaired GD-ROM.

gdi-utils gui Dreamcast
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gdi-utils gui Dreamcast

Now is the time to recreate the complete GDI file.

To do this, create an empty folder on the disk. I named it "DATE".

We put all the batch files from the game folders into it, keeping the org. paths, names etc.

Of course, also those modified by us - it is logical.

We are not allowed to hack boot files such as 1ST_READ.BIN and IP.BIN (e.g. with LazyBoot) to the selfboot form (allowing to run them in DiscJuggler images and on CD).

Then run GDIbuilder and select our folder in Data Files option.

We indicate the location of our IP.BIN file.

We mark the window / checkbox Output raw sectors (2352 mode) and click Create GD-ROM.

If you have unchanged audio tracks (RAW), do not add them to the CDDA window.

The program will create a new track, track3.bin, which should be moved to the folder where there are RAW, BIN tracks and disc.gdi file

GDI builder Dreamcast
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GDI builder Dreamcast

The GDI file created in this way guarantees that all emulators (Redream, Demul, NullDC, Flycast, Reicast etc.) as well as the GDEMU or USB GD-ROM installed in the console will be opened correctly. The game will also not freeze at startup. The rest of any modified files are the part that I am not able to verify if they are correct. This includes translation, editing, and other mods.

That's it. I hope that, as usual, I helped you and encouraged you to work on your own projects.

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