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


  1. Larry

    Well, I got a 512MB NetDimm with zero key pic off eBay all the way from Portugal, plugged it in and… nothing. No sound or video. Supposedly it’s 100% ready to go and works properly. They used the picture you have at the top of the page for the listing and it really does look clean and is in great condition. I have a bios chip 21576H installed in the Naomi 1 machine. I even hooked it up to a monitor but the monitor receives no signal. The MvC2 machine I have uses a 15k monitor so I thought it was that until I plugged it into a PC monitor. Bummer. At least I can return it. Any ideas? I was so hoping this would be an easy install.

    1. 8bitplus (Post author)

      Hi Mate, yeah that does not sound right. So your Naomi works fine with the MvC2 game cartridge? if so don’t change any DIP settings on the Naomi. the NetDimm should just plug in and display the Network screen when powered on.
      Where are you based? would you like to send the Dimm to me for testing? Send me an email through the contact page above and we can talk more. Neil

  2. Larry Whittaker

    Awesome! Thank you so much for your super quick response.

    I was hoping using the LAN to flash would be fine because I’d eventually like to create a script from my Hyperspin cabinet that flashes the MvC2 machine when a certain game is selected. In other words, one would select a game from the Naomi HS wheel and it would then flash the MvC2 machine sitting next to it for play.

    1. 8bitplus (Post author)

      Ok yes that’ll work fine. You might want to have a look at my raspberry pi I use to flash the dimm. It has all the games on an an SD card.

      1. Larry

        I do have one more dumb question. Does the net dimm support only Naomi games or can it do Sega Triforce and Atomiswave games too. The reason I ask is because the BIN files for the different systems are often found with each other and Atomiswave games say Naomi Conversions. Thanks, again.

        1. 8bitplus (Post author)

          Yes, you can play the Darksoft converted Atomiswave games on the Net Dimm with a Naomi or Naomi2 motherboard. Triforce games will only work on the Triforce board.

  3. Larry Whittaker


    Thanks for posting this tutorial. I’m looking to eventually get a Naomi NetDimm off eBay but want to be sure I am doing the right thing. I have a Marvel vs Capcom 2 machine. About 2 years ago I go a bios chip 21576H and installed it into my Naomi 1. I had a few questions:

    1. Is the standard power supply in a MvC2 with a 29″ monitor enough for the NetDimm to run properly or should it be upgraded? I ask this because I saw a video saying it should be upgraded if using the CF mod. I’d rather just use the netboot method.
    2. Can the NetDimm be flashed over a LAN connection from a PC on the network or can it only be done with a crossover cable connected directly to a PC?
    3. If a router is used, does it matter what the IP address that the NetDimm is given. I see people use or something similar but does it matter what subnet or IP the Naomi is on?
    4. if using a LAN is OK, should only a wired network be used?
    5. I understand that a wireless can drop the signal so if it did, would this brick the NetDimm or is it recoverable (or any bad flash for that matter)?

    Thanks for your response. I look forward to hearing from you.

    1. 8bitplus (Post author)

      Hi there.
      1. The standard psu will be fine. Mine is the original and worked perfectly for years.

      2. Yes the dimm can connect to a router with normal cat5 cables. Crossover needed if direct to pc/laptop.

      3.You can give the netdimm any ip address in your current range. Just pick an ip that nothing else is using.

      4. I guess you meant wireless?? That’s fine too. You can go from wireless laptop or over access points if needed. You can also connect the Naomi to a wireless bridge if needed.

      5. If the signal dropped when sending a file nothing bad will happen. The file transfer will just fail, then you send again. You cannot brick the dimm that way. The RAM is just pc ram and not flash ram.

      Hope that helps. Let me know if you have any more questions.


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