Netboot Sega Naomi NetDimm


Project to get the netboot feature working on the Naomi arcade system using a Raspberry Pi computer board. Overview of the process, equipment and software required. No links to ROM images will be provided.


Netbooting refers to the loading of an arcade game image over a wired network.

The Sega Naomi system made use of game cartridges originally, then lower cost and easier to produce GD-Rom disc’s. the GD-Rom systems are fairly reliable (as with the Dreamcast) but still has a few drawbacks. The drives rely on moving parts that can fail, and a physical copy of the game needs to present in each cabinet.

Towards the end of the Naomi systems life, Sega produced some large multi-player games like Derby Owners Club (made use on 10 Naomi’s). In a “satellite” setup each screen was controlled by a Naomi board, and they all communicated with each other by fiber optic connections.

Instead of having to load the game from disc for each machine, the arcade operator could “push” the game out to each Naomi. this was done over a LAN network to a special cartridge module called a Satellite Dimm or NetDimm.


The NetDimm was a replacement for the standard GD-Rom Dimm used to connect the Naomi to a GD-Rom drive. The GD SCSI connection was retained with the addition of the RJ-45 connector.

Switching between NetBoot and GD-Rom boot is done by changing a set of jumpers located under the top metal plate.


GD-Rom security takes the form of a chip inserted into the NetDimm. It contained the data needed for decryption of the protected game on the disc.

Nothing changed with this for the original netboot methods of the arcade operators. The security chip for each game wound need to be present.

With home NetBooting this is no longer necessary. The solution is a “Zero Key” chip. Effectively just a blank key that can be used with the fully decrypted roms found online. The chip is not hard to find if you look.

Netboot Requirements

To transfer games from a PC, you will need:

Item  Note
Working Sega Noami 1 or 2 arcade system  Up to date Bios Japan, or Export
Netdimm module  Firmware 4.01 or 4.02
Zero Key chip  Use Google
Transfer software  Use Google
Game images  No help from me. Sorry.
PC or laptop with RJ-45 connector  Windows XP or higher. Linux.
RJ-45 crossover cable  Any length needed

Make sure your Naomi has a recent BIOS chip that supports the Netboot. Find them here:

AndyGeezer, or Giz10p.

I use version EPR-21578H for Export. It boots almost all the games I’ve tried. If your bios is too old it might not recognize the NetDimm.

Setup Network

On your PC/Laptop, set a static IP (i used for the LAN network adapter. Netmask should automatically set to

Next connect the NetDimm and enter Test Mode.

Under the network settings, set a static IP Address. Something like will work fine. Set the same Netmask as the PC

Save settings and turn the system off and on again.


Now your network setting are in place you can connect the laptop to the NetDimm and send the game data.

In a command windows (cmd) enter the transfer.exe, IP address of NetDimm and the game image then hit Enter.

eg. “c:\netboot\transfer.exe ggxx.bin” 

For the above example software and ROM image are located C:\ in a folder called “netboot”

The first thing that happens is that the software transfers the game data to the NetDimm storage. This can take some time depending on the size of the Rom.

When transfer completes, Naomi will reboot then check the game data. Progress is also displayed on the PC screen.

When checking has finished, the board will reboot once again and start the game.

You can now disconnect the laptop/PC if needed, and enjoy the game.

To load another game just start another transfer. The Naomi should reboot and start receiving the new data.

So there you go. Guilty Gear XX loaded. Its a good alternative to setting up the GD-Rom system, and handy if you have a PC/Laptop in reach of the arcade cabinet.

If you don’t want to connect to a PC you can always install a Raspberry Pi to transfer the game image.

Raspberry Pi Netboot

Thanks for reading, any questions or comments welcome.

8bitplus 2015

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