Sega Naomi Maintenance: GD-Rom Swaps (Error 24) and Arcademodbios

Naomi Error 24/GD-Rom Swaps

So a couple days ago I got a new Naomi game in the mail, popped it in and was greeted with a nice Error 24 (GD-ROM NOT FOUND). I figured something wasn't hooked up properly so I reseated all of the connections from the psu to the GD-Rom, as well as the SCSI cable going from the GD-Rom. Nothing worked? I reseated the Dimm board as well as cleaned the disc and laser lens. Error still persisted. I read online that this error is either the lid on the drive is not closed properly (which wasn't the case), the disc wasn't present, or the drive died. I was kind of mad now that I would have to spend another $75-$150 on a "new" Naomi GD-Rom drive.

Of course me being as I am and not giving up on anything until every repair option had been exhausted I did some research. I learned that the laser assembly from a Dreamcast could be swaped into the Naomi GD-Rom unit and it would usually work. So I threw both of them on the table and proceeded to take them apart. I removed the GD-Rom drive assembly from the Naomi unit, and repeated the process on the Dreamcast. I heard there are two different drives used in a Dreamcast, Mine was a Revision 1 so the drive was 100% the same as the Naomi Unit. The ribbon cable in the Naomi unit must be reused as the Dreamcast's ribbon is much to short. The power cables (2 small connectors) make the trip with the gd-rom assembly as they are the same on both systems. The hardest part was getting the ribbon cable from the Naomi into the Dreamcast's laser assembly. A trick that I figured out was to undo the screw holding the metal rail in place that the assembly glides on. You pull the rail out, slide the laser assembly off of it making it much easier to get that ribbon cable inserted into it. Once done I placed the assembly back on track (ensuring the small spring that was under the rail was put back in place), and reinstall the rail and screw.

I was figuring it had almost no chance of working as I do not consider myself an expert by any means. So I went back to my Naomi setup and hooked up the drive. Turned it on and sure enough, no Error 24. The system went right into checking memory, and started loading from the GD-Rom drive. In a minute or two I was seeing Lupin III The Typing on the screen again (figured I would use that game as I knew it worked). Just incase you were wondering, when the error would happen it would quickly say Naomi GD-Rom System and then go right to Error 24 without checking memory. So now, all I have to do is replace a $10-$30 Dreamcast, which is much more common then a Naomi GD-Rom unit. So if you ever have this problem, grab a Dreamcast and fix it yourself.

Naomi Arcade Mod Bios

Other then this problem, Which had just happened a couple days ago, I had another "problem" with Naomi. Some games that I own (such as: Virtua Fighter 4 Evolution Ver B, Guilty Gear XX # Reload, Melty Bloody Act Cadenza Rev A) needed to be run on Japanese Bios and some games (Such as the Initial D Games, since they are the English exports) Need to be run on USA bios. Also some games will change a bit depending on what Bios is installed (example Gunspike (Japan) becomes Cannon Spike (USA) and Moero! Justice Gakuen (Japan) becomes Project Justice (USA)). Plus most of the games that are compatible with the Dreamcast controller ports need Japanese bios. My solution I had in place was to buy a Japanese bios chip and swap them when needed. Only problem here is every time I pulled out one of these chips I bent the pins a little and had a feeling that after a while one of them would break or I would do damage to the Naomi 2 board in a botched attempt to remove the bios chip.

Enter ArcadeModBios. This is a bios chip for the Naomi or Naomi 2 which allows you to switch regions with a combination of dip switches 3 and 4 (which are unused otherwise). I had heard about this because someone on KLOV forums was selling a Naomi unit which hard these bios and briefly mentioned how it worked. I of course had no interest in getting his Naomi 1 unit but quickly found out that there was a version for Naomi 2 as well. The cost was about $30 for the chip shipped. Took a good month and a half to get here because unfortunately the first one he had sent got lost in the mail, but you know, those things happen. Finally got the bios chip on this past Saturday and all is well. I can easily switch from Japan Mode (3 and 4 off) to USA Mode (3 on 4 off) with just the flip of a switch without needing to completely disconnect the Naomi system or rip the bios chip out every time. So I highly recommend if you have a Naomi or Naomi 2 system at home and have games that require different bios, get yourself a Naomi Mod Bios chip.

Arcade Mod Bios dip switch settings (I received version 1.15)


Update: Many days later for the heck of it I plugged in the Dreamcast which now had the "bad" Naomi GD-Rom drive installed in it and to my surprise it works without problem. I tried about 5 Dreamcast games and all load and play without problem. I also tried Bleemcast Tekken 3 disc and even that worked without a problem. I can honestly say I can not understand why it works, perhaps there is something wrong with the GD-Rom drive that makes it not work in Naomi but does not prevent it from working on a Dreamcast console. Go Figure.

Sega Model 2A CRX and Model 3 Step 1.0 Differences and Similarities

At this point I own both Sega Model 2A CRX with Virtua Fighter 2 and Sega Model 3 Step 1.0 with Virtua Fighter 3. Both of these games were the marquee game for their original hardware revision and it only got better after that. Later steps and revisions had faster processors and more horse power. Having these to pieces for a few weeks now I have noticed a few things that are quite similar and some things that are very different between the two. So here they are:

Similarities:

• Made up of 3 Boards (Graphics, CPU, Rom)
• Both use Martin Marietta/Lockheed Martin Real 3d Chips
• Use the same 25 Pin input connector
• Display video in medium resolution (24kHz)
• One power connector matches (10 pin ground & +5v)
• Board stacks in metal cases fan cooled
• Use the same Video (5 pin) and Audio (4 pin) Connectors
• Output unamplified audio (Amplifier or Amplified Speakers needed)
• Socketed roms make for easily upgrades (VF2.1/VF3TB)
• Earlier games do not use security boards (Later games like DOA do)
• Neither game got an arcade perfect port (same goes with the first 4 games)
• A Model 2 will work in a Model 3 Cabinet as long as you connect the 24 Pin to the proper pins

Differences:

• Model 2 uses an Intel cpu (i960), Model 3 uses a PowerPC cpu (603e)
• Model 2 uses another 10 pin (+5v & ground), Model 3 uses a 24 pin for more power (+3.3v, Ground & +5v)
• Virtua Fighter 3 uses an additional button (pin 12 on model 2 harness)
• Model 2's fan connects externally, Model 3's fans (2) are internal and connect to the filter board
• Some Model 3 Boards (like mine) have a vga port right on the filter board
• A Model 3 will not work in a Model 2 Cabinet without a different power supply (one with +3.3v)

Sega Model 2a Board (with cage and filter board


Sega Model 3 Step 1.0 Board

Sega Naomi and Naomi 2 Hardware Information

The original Naomi is the arcade version of Sega Dreamcast. It has twice the graphics and system memory compared to the console and 4 times the audio memory. The reason for such a jump in audio memory is because the system does not stream cd audio off of a disc like the dreamcast but rather it runs the audio off of the rom chips or dimm board. Speaking of which, the Naomi games come in two forms. Some games will come as a rom cartridge and some games will come on GD-Rom disc which require a dimm board and gd-rom drive.

A Naomi System with Cartridge (Virtua Tennis)


The Rom cartridges are large rectangular cartridges with the name of the game on the top and 3 connectors on the bottom where the cartridge connects to the board. The benefit of this format is there is almost no load time since the game does not have to be read from an optical disc like its console brother.

A Naomi Cartridge (Dead or Alive 2):


The GD-Rom games do not work the way you would think. On the Sega Dreamcast the game would be read and loaded off of the GD-Rom disc in real time, however on Naomi to save on load times, when the system is loaded the entire game is loaded onto the dimm board. Think of the dimm board like a Naomi cartridge that instead of having permanent rom chips it has fully rewritable ram. Once the game is loaded into this dimm board the gd-rom drive shuts down and just like the cartridge games, there is almost no load time once in game. Loading a game from gd-rom to dimm board can take about 3-5 minutes depending on the size of the game. In order for the game to be loaded you must insert the proper security key chip into the dimm board, if the wrong chip or no chip is inserted the system will display an error code and not load. Dimm boards have a battery pack which makes them able to keep the game saved in the dimm board for 72 hours with the arcade machine off. Unfortunately these days the battery packs are either rare or expensive and most operators opt to just let the game load every time. As long as the cabinet/system is not turned off even with a dead battery the game will continue to run.

A Naomi GD-Rom Game (Guilty Gear XX)


A Naomi GD-Rom Drive


As far as input goes, like the 246, The Naomi uses JVS I/O boards plugged into the usb like connector. There are a few boards this system can use depending on the game you are running. For standard games that use just a joystick and 1-6 buttons a Sega JVS to Jamma I/O will work just fine. Some people prefer the more expensive Capcom I/O board but for 2 player games that just use standard joysticks and buttons (no excessive analog controls), the Sega board is inexpensive and works just fine.

Sega JVS to Jamma I/O Board


The board will connect directly to the 6 and 8 pin plugs of a JVS power supply which when used at home will either need an adapter or to be modified in order to connect it to the wall outlet. When using the GD-Rom drive you will need a splitter which either connects to the 8 pin as a pass through or connects to the smaller connector. Your GD-Rom drive will connect to the dimm board with a normal SCSI cable. The video can be connected directly to the vga plug on the front and will output to any vga compatible monitor as long as dip switch number 1 is set to the up position. The audio is connected into standard red & white composite audio plugs like most jvs systems and of course is unamplified so an audio amp in an arcade cabinet or amplified speakers will be needed to hear the audio properly. Unlike other JVS systems the Naomi only has one VGA port and one set of audio jacks (most jvs systems have 2 of each for vs play).

Front of the Naomi (showing filter board)


JVS Power Supply with the 3 Mentioned Plugs


The Naomi 2 is an upgraded version of the original Naomi. It has dual processors and dual graphics chips. It has the same amount of system memory as Naomi but double the graphics Memory, having 32Mbyte for each GPU. Each graphics processing unit renders one half of the screen. The best part about this system is it is fully compatible with all original Naomi cartridge and GD-Rom games along with having its own graphically enhanced games. Of course it goes without saying that a Naomi 2 game will not work in an original Naomi system. All interface and connections are exactly the same as the original Naomi so upgrading from a Naomi to Naomi 2 is very easy. The original Naomi cartridge games are the white/cream color that matches the system where as the Naomi 2 cartridges are the grayish beige that matches that system. The GD-Roms will be noted as working only on Naomi 2 on such games like Initial D, Beach Spikers, Virtua Fighter 4 and Virtua Striker 3.

A Naomi 2 System with Dimm Board


A Naomi 2 Cartridge (Club Kart European Session)


Some games such as Initial D need more analog inputs then a standard I/O can provide. Infact the game will not even boot unless a Sega JVS Type 1 I/O is present, the system will just reset without that board. Since Initial D uses a few more analog controls (Steering wheel and pedals) then the normal I/O could handle that is why it is locked out in such a way. I will have more on Initial D on its own page.

Sega JVS Type 1 I/O Board (type 1)


The one of the last Naomi topics (for now) that I would like to discuss is region protection. For the most part, most Naomi and Naomi 2 games will work just fine regardless of the bios that your system has installed. However, certain games will only run on certain Bios. For instance, Initial D english versions require either USA or Export Bios and will not run on Japan bios. Games such as Virtua Fighter 4 Evolution (Ver B), Capcom VS SNK Millennium Fight 2000 Pro, Melty Blood Act Cadebza, Guilty Gear XX #Reload and Street Fighter Alpha 3 Upper will only run on Japan bios. Other then the region restrictions there are some games that will not only fully translate themselves but also change their name depending on the bios. Moero! Justice Gakuen (Japan Bios) will change to Project Justice on USA or Export Bios just like Gunspike (Japan Bios) will become Canon Spike using USA or Export Bios. The best part is that the bios chip is socketed so no soldering or desoldering is required to switch it out.

One last thing that often gets people confused is that some Naomi games are able to use Dreamcast controllers. Not too many games support them and you must have a Japanese Bios installed. The only game that I have come across that will work in USA bios with the controller is Mobile Suit Gundam Federation vs Zeon (and the DX Version). Capcom was a company who supported this feature a good deal, infact many of their cabinets have a controller port right on the control panel. Games such as Moero! Justice Gakuen, Marvel Vs Capcom 2, Street Fighter Alpha 3 Upper, Gun Spike and Power Stone all support this feature in Japan bios. Games such as The Typing of the Dead, Lupin III The Typing and La Keyboard can use a Dreamcast keyboard using this same port. The filter board (that board on the front with all the ports) has pin headers marked CN6 and CN7. The first five pins of each of these are for the controller adapter. The official adapter that would come off of a control panel will be a full JST (Japanese Solderless Terminal) connector going across all pins even the unused ones. You however can get a 5 pin JST nh connector and splice it to a dreamcast extension cable eliminating the need to hack up any Dreamcast controllers and giving you the ability to swap in a Keyboard if you plan to play those games. Some games such as Moero! Justice Gakuen even have the ability to share data from the Dreamcast (Japanese of Course) to the Arcade Version. In this game your custom character made in the console version can be used in the arcade version if you bring your controller and memory card.

Dreamcast controller ports in a Japanese arcade:

Namco System 11 and Namco System 12 Arcade Information

Namco System 11 is a standard jamma board which is Namco's arcade version of the Sony Playstation. The board includes a standard jamma edge connector as well as a 48 pin edge connector which is used for additional buttons in some games such as kicks (hence the common "kick harness") or even block in Soul Edge. The additional connector is also responsible for the second channel for stereo sound (since the jamma harness is mono). This board is capable of only Standard resolution 15kHz video through the jamma edge. Notable games on this board are Tekken, Tekken 2, and Soul Edge (prequel to Soul Calibur)

The board is made up of three different board interconnected together. The base board, also known as the main board, contains the main program and sound roms that make up the game. The larger of the two sub boards, also known as the cpu board, As the name would make you think, houses the cpu and all of the system ram. It sits on top of the main board. The final and smallest board, also known as the rom board, contains all of the game's graphics roms. Since all of the roms are surface mounted it makes changing a board from one game to another nearly impossible. This however was not a problem due to the much lower cost per board compared to other hardware of the time such as Sega's Model 2.

The Namco System 12 (in the same vein as Namco System 256) is an upgraded version of the System 11. It features more memory and faster processors. Unfortunately the exact changes are not known at this time. This board made it possible to have much better graphics and more fluid animations in games such as Tekken 3, Tekken Tag Tournament and Soul Calibur. This new board also added full jvs compatibility. It however is still compatible with jamma and the 48 pin "kick harness" but it also gave the operator the option to connect vga video at 24kHz (dual vga for dual displaying like a normal jvs spec), as well as the 6 pin jvs power supply plug and the usb looking connector for a jvs i/o. When a Jvs i/o board is connected the 48 pin harness is not required anymore for your extra buttons as they connect directly through the i/o. The other thing that is added are two pairs of composite (red and white) audio plugs which are not amplified so you will either need a set of amplified speakers or a sound amp board.

As far as connecting these boards at home goes, all you will need is a standard Min Dong, Suzo Happ or other screw terminal power supply and matching jamma harness. Of course a 48 pin connector will be needed for the extra buttons used in most of the games (Kicks in Tekken and block in Soul Edge). When using a System 12 board as mentioned above it can be plugged directly into a JVS setup, but without need for the 8 pin power connector that many jvs power supplies have. Another interesting thing is that Namco System 12 board are fully compatible with Namco's Cyberlead cabinet and will display special messages on the led display while the game is playing. A special note, if you are connecting either Tekken Tag or Tekken 3 with a Sega JVS to Jamma I/O, Button 3 is used for Tag in Tekken Tag, however when connecting Tekken 3, Skip button 3 and connect the Button 4 and 5 for the Kicks.

Namco System 11 Board (Tekken 2)


Namco System 12 Board (Tekken Tag)



Tekken Tag Tournament running in a Cyber Lead Cabinet