Arcade Systems

Sega NAOMI Introduction

The NAOMI (New Arcade Operation Machine Idea) from Sega is an arcade system based on the Dreamcast that became available in 1998 and succeeded Sega's Model 3 series. The similar architecture between the NAOMI and Dreamcast include a Hitachi SH-4 CPU (running at 200MHz), Yamaha AICA sound, and a different version of the PowerVR Series 2 GPU. Where the NAOMI out performs the Dreamcast is in having double the system memory (32 MB VS. 16 MB) and double the graphics (VRAM) memory (16 MB VS. 8 MB), four times the sound memory (8 MB VS. 2MB) and updated PowerVR GPU with better performance.

Despite having a successor in the form of the NAOMI 2, the original NAOMI lasted longer, seeing use up until 2009. Other forms of the Dreamcast in arcade form include the Atomiswave which is more closer to a Dreamcast than the NAOMI although still with better specification than the Dreamcast; many Atomiswave games have been unofficially ported to the NAOMI. There is also the Sega System SP and Sega Aurora which are also based on the Dreamcast/NAOMI systems.

Here is the top view of a NAOMI:

Multiple NAOMI boards can be stacked together in what is known as a Multiboard setup, which was designed for more graphic intensive games or for driving multiple monitors, with an example of a game that uses this arrangement being F355 Challenge. Another unique configuration comes about from having multiple NAOMI systems linked to a master NAOMI and this arrangement is known as a Satellite setup and Derby Owners Club is an example of a game that uses this setup. YouTube user propcycle shows Derby Owners Club in action which can be seen at:

https://youtu.be/2qVXhE8eRFk

GD-ROM

Some NAOMI games came in cartridge format which fit on top of the NAOMI main board, featured up to 448 MB of memory and fast loading times, but were expensive. To lower costs, games were also released on Dreamcast-like GD-ROM discs, offering up to 1GB of storage but with significant loading times. As the NAOMI is primarily cartridge based, NAOMI supported GD-ROM based games via an external GD-ROM unit plugged into a DIMM or NetDIMM cartridge via the SCSI connector. Essentially, a NetDIMM is very similar to a DIMM cartridge but in addition to the SCSI connector also has a RS-232 style connector (to get debug information once enabled) and ethernet port too to allow booting games from a network.

In the photo that follows you can see a top-down view of a NAOMI GD-ROM drive (note that all NAOMI GD-ROM drives are blue, matching the colour of the NAOMI 2: see NAOMI 2 section further down the page). The drive has quite an odd shape to it, and because of the rough environment that arcade machines are typically found in the drive lid is normally screwed down (you can see, however, that the truss screw is missing).

Removing the lid reveals pretty much what you would expect: the CD mechanism which is very similar to the GD-ROM drive found in a Dreamcast and can be interchanged.

At one side of the drive is a SCSI-2 connector for interfacing to the NAOMI via a DIMM/NetDIMM cartridge (you can use a standard SCSI-2 male-to-male cable but it must be under 2 feet) and the power connector on the tight:

You will need to either use an original power cable or make up your own and depending on your power supply it may be able to provide enough power for the GD-ROM as well as everything else. I was successful in putting together my own cable and powering the GD-ROM off the same power supply powering my NAOMI 2 system. Pin 1 of the power connector is farthest from the SCSI connector and here is the pinout:

1 & 2: 12V

3 & 4: 5V

5 & 6: GND

Here is a link to the NAOMI GD-ROM manual:

http://sega-naomi.com/resources/manuals/gdrom-manual.pdf

Don't forget if using a NetDIMM to put into GD-ROM load mode by changing these jumpers:

JP1 and JP2 2-3, JP3 1-2.

When the NAOMI starts up the game is read from the GD-ROM into the DIMM/NetDIMM's internal memory (standard Non-ECC SDR-DIMM RAM) which the game then runs from. In this way there is less wear and tear on the GD-ROM disc, better loading times when playing the game but initially it's quite a slow process to load the game from GD-ROM. The GD-ROM games come with a security 'key' (actually a PIC microcontroller) which must be plugged into the DIMM/NetDIMM for the game to load although it is possible to obtain a universal 'Zero' security key.

Fortunately, the DIMM/NetDIMM cartridges feature a rechargeable battery which will keep the game in memory for a day or so after the NAOMI is turned off (the battery is not required and without it you just have to load the game again when booting the NAOMI). The GD-ROM unit can also be used with the Triforce (arcade system based on the Gamecube) and Chihiro (based on the first Xbox).

In the photo that follows you can see the DVD size clear case (note: no artwork) containing a NAOMI GD-ROM game disc Sports Jam top right; note the red colouring which contrasts with Triforce GD-ROM discs which are purple. The service manual (gives instructions how to set up and operate the game) is on the left and the security key bottom right.

Curiously, if you try to play a NAOMI disc in a Dreamcast as a music CD you get a warning in both Japanese and English that the disc is only for the NAOMI system and is to not to be used in a Dreamcast and to not play in a CD player. On a related note a Triforce GD-ROM when put in a Dreamcast does not mention the Dreamcast presumably because by the time the Triforce was released the Dreamcast had been discontinued.

My GD-ROM drive I bought as non-working in the hope I could fix it but it looks like someone else already attempted a repair and possibly broke it. Take a look at the unit with the top cover removed:

At the bottom of the photo above you can see a small fan (note the rust) which seems odd as you would think the electronics wouldn't get that hot but perhaps the fan's purpose is more to keep the internals free of dust; the fan is similar to the main system fan found in a NAOMI1/NAOMI2. Top right is the switch which detects when the GD-ROM lid is turned securely in place (the switch is pushed outward when the lid is in place). Toward the bottom and to the right you can see an orange-brown flat flex cable which had already been torn and to the right of the cable is a screw which has been put back at an angle. While the flex cable that connects to a Dreamcast GD-ROM has the same number of conductors it is far too short but fortunately I happened to have a very similar cable I had taken from something else to use as a replacement.

The main board of the NAOMI GD-ROM unit is quite different to its Dreamcast counterpart, sharing only one main IC. It can be seen below along with the GD-ROM assembly:

On the main board at top left can be seen the power connect and the SCSI connector to the right, and bottom middle is the connector that accepts the flex cable from the GD-ROM assembly. The lid switch is on a 3-way connector (red & white wires), the laser assembly motor is on a 4-way connector (black & red wires) with its limit switch using 2 white wires, and the disc motor is on a 2-way connector (black & red wires).

Unfortunately the torn cable was not the only fault as the original listing for the sale of the item mentioned a power fault. If you look at the circuit board above you can see that the BA5986FM CD/DVD-ROM motor driver IC (bottom right) has been damaged. This meant that there was a short across the 5V and 12V power inputs as well as a short to ground which would certainly explain the power supply fault. Speaking of power, a 78M05 (seen bottom left in the photo above) 5V regulator is used to derive 5V from the 12V line even though 12V is already provided; possibly the reason for the regulator is to provide more current on the 5V line without loading down the 5V power input too much.

I later obtained another faulty GD-ROM drive unit which was supposedly could be detected by a NAOMI but wouldn't load any games so I took it apart and found it to be in a bad state. There were was rust and the fan was so clogged up it wouldn't turn so I changed it for the fan from my other GD-ROM drive unit. I had a look at the PCB of the second GD-ROM unit and did some basic tests running it on my bench power supply. With the fan running but no disc spinning (there is no movement of the laser assembly or spinning of the disc without connection to a NAOMI) 170mA was being drawn on the 5V line and 230mA on the 12V rail.

Even though at this stage the GD-ROM was in pieces but connected together I connected it up to my NAOMI and forced the lid switch down by resting a screwdriver on it, and to my surprise the game was loaded. Replacing the fan didn't fix the problem as I didn't have the fan connected at this stage but perhaps re-seating the connectors helped. An issue I did have was that first time trying I got 'ERROR 26 OPTION BOARD IS MALFUNCTIONING'. It turned out the problem was that I had to put the security key that came with the game into the NetDIMM even though I already had a so-called Zero chip installed which should work with all games (and certainly works when transferring games over ethernet using the official Sega transfer program).

Some other errors you may encounter and what the mean, starting with 'ERROR 25 CAN NOT ACCESS GD-ROM DRIVE', which means the DIMM/NetDIMM is set to load games from GD-ROM but the GD-ROM drive cannot be detected so check the SCSI and power cables. Another error is 'ERROR 24 GD-ROM IS NOT FOUND': this happens if you don't have a disc in the drive or there is a problem loading from the disc (it's scratched/broken).

Network Game Loading

A game can be loaded into a NAOMI by using a NetDIMM add-on cartridge with a Zero key installed which lets games be transferred to the NAOMI via the NetDIMM's ethernet port with the aid of a computer and a special transfer program. This provided great convenience to arcade operators as it reduced the need for a physical copy of a game especially helpful with multi board setups, such as with Derby Owners Club which used 10 NAOMI boards.

For further information about loading games over the network please see:

http://8bitplus.co.uk/projects/netboot-sega-naomi-netdimm/

It is also a popular choice to use a Raspberry Pi to load games into the NAOMI with either an LCD and switch module interface or web based interface to select a game to load. Please see this site for more information:

http://8bitplus.co.uk/projects/netboot-with-raspberry-pi/

Note that by using a Raspberry Pi there is no need for a Zero key to be installed in the NetDIMM.

Compact Flash Game Loading

It is also possible to load games from a compact flash card using either an official CF reader or a homemade alternative, which essentially emulates a GD-ROM drive. Check out this video tutorial which explains how to make your own CF reader (note that there were, however, official CF readers for the NAOMI):

https://youtu.be/Zb6hP7WStSM

Here is some information about the CF boot process:

http://wiki.pcbotaku.com/wiki/Naomi_CF_boot

Games

Games for the NAOMI include The House of the Dead 2, Crazy Taxi, Dead or Alive 2, Power Stone, Virtua Tennis and Monkey Ball, all of which (excluding Monkey Ball although a Dreamcast port was apparently in the works) were ported to the Dreamcast.

The following screenshots are from Power Stone, Sega Tetris and Virtua Tennis:

NAOMI Dreamcast Peripheral Support

Some NAOMI games support one or more Dreamcast peripherals and they will be listed in this section along with the supported peripherals; support for Dreamcast peripherals has to be enabled in the game's test menu (Japanese BIOS needed). Four Dreamcast controllers can be connected to a Naomi using connectors CN6 and CN7.

I have put together a list of supported Dreamcast peripherals mainly from the following sites but please note the information may be incorrect:

https://forum.arcadeotaku.com/viewtopic.php?f=2&t=26535&p=366637&hilit=Vmu#p366399

https://forums.shoryuken.com/t/the-sega-naomi-thread/167791/129

Akatsuki Blitzkampf Auf Asche: controller

Border Down: controller

F355 Challenge: VMU

F355 Challenge 2: VMU

Heavy Metal Geomatrix: VMU, controller & rumble pak

Illvello: controller

Karous: controller

La Keyboard xyu: keyboard

Lupin the Typing: keyboard (jpn/usa BIOS)

Mobile Suit Gundam Federation VS Zeon: controller (jpn/usa BIOS)

Mobile Suit Gundam - Federation Vs Zeon DX: Controller

Moeru Justice Gakuen: VMU & controller

Musapeys Choco Marker: controller

Radirgy: controller

Senko No Ronde New Version: controller

Senko No Ronde SP: controller

Spawn: In the Demon's Hand: controller, VMU & rumble pak

The Typing of the Dead: keyboard (jpn/usa BIOS)

Toukon Retsuden 4 - Arcade Edition: VMU

Virtual On Oratorio Tangram VER.5.66: VMU

NAOMI Wiring up I/O

Aside from connecting Dreamcast peripherals to a NAOMI via the Maple bus connections (for the games that support it) you will need to use some form of I/O board which connects to the NAOMI USB connector (although not actually using the USB standard protocol). The I/O board needs to be powered and will typically provide a number of digital and analog inputs as well as outputs but which and how many are used will depend on the game. You can get information about an attached I/O board by entering the main test menu (press the test button) and then selecting JVS test as you can see below:

To test inputs you can then select input test and for every button pressed you should see a single value change from 0 to 1 for each player. If you have a coin switch wired up pressing the switch will increase the coin value with every press. The input test is shown in the screenshot that follows:

Games will also have their own test menu which can be accessed from the main test menu by selecting game test mode. Each game will have its own set of test menus which will likely include options to test inputs (useful to make sure you have enough working inputs to play the game) and outputs (such as lights). For example, you can see Power Stone's input test below:

Getting inputs to work is as simple as wiring up switches to each input of the I/O board and using a common GND connection. If you are not using a cabinet with built-in controls for the switches you could modify an existing arcade stick. However, you could also wire up a console controller but depending on which controller you use will determine how difficult the wiring will be. With a Mega Drive controller, for e.g., you will need to supply 5V to the controller and you also need to handle the select input to be able to read all the buttons. You could remove the controller's 74HC157 multiplexer IC and rewire so the buttons go direct to the controller lead, however.

More modern controllers can be difficult to work with as they use a controller IC (which is may be the COB type and thus difficult to remove) and to make a direct connection to a switch you'll need to scrape away part of the circuit board track of a switch and solder to the exposed copper and that can be tricky. I ended up using a Gamster Xbox original controller which had some advantages to other controllers I had looked at, such as the standard Dreamcast controller. The Xbox controller had the Dpad on a separate board so it was a matter of isolating it from the main board and soldering wires directly to the Dpad board. The 6 main action buttons had what looked like test pads leading to the COB IC so I was able to solder to those pads. I did have to solder to the back and start button pads but pressing those buttons fortunately weren't hindered by the wires I had attached. Unfortunately I did end up having to break all the tracks from the buttons to the COB IC as otherwise the buttons (aside the Dpad buttons) were acting as if they were pressed as even though the IC wasn't powered it was still interfering.

I ran 15 wires out of the controller, giving me access to all of the controller's 14 buttons, more than enough for most NAOMI games. While not ideal to have so many wires coming out of the controller it was the only way without encoding the buttons and decoding at the other end. At the end of the wires I used a DA-15 connector as I had a breakout board to use with DA-15 type connectors. A VGA cable is a possible alternative but those cables tend to be thick, often not all pins are used (but enough for a good number of switches), and the wires themselves can be very thin making it difficult to solder to.

The I/O board I have been using is a Sega board labelled as 837-13551 which I found some information about at this site:

http://triplemoonstar.brinkster.net/theshed/default.asp?stockid=1718

It has the pinouts of the board for the power and interface connectors. You will need to power the board using CN7 (5V power in) and CN1 (12V power in), although only 5V is needed if you just connect inputs to the board. From my tests having the I/O board connected to the NAOMI and nothing connected to the I/O board, the board draws around 80mA, with a peak of 92mA, on the 5V line, and nothing on the 12V rail which is to be expected.

Analog inputs can be connected to the I/O board using CN6 whereas digital inputs and outputs are to be wired to CN3. Originally I used a wiring harness that had come with the NAOMI when I bought it and that worked fine but when I connected my own wires directly to the I/O board I couldn't get any digital inputs to be detected and the coin count displayed as 8000 for both players. I already knew how to fix the coin issues as you have to wire a (roughly) 100R resistor from 5V to pin 49 (coin meter 1) and also to pin 50 (coin meter 2) as mentioned on the site linked above. It was odd, however, why inputs were no longer detected and the only thing that stood out was that pin 1 and 3 (which both should be +5V) of CN3 were connected together. Nevertheless I found with my multimeter that pin 1 was way below 5V and by connecting pin 1 and 3 together inputs were now detected again. I conclude that the pinout for CN3 on the site linked above is not totally correct. Looking at the Jambo! safari manual's wiring diagram they are using the same board as me and pin 1, 2 and 3 are connected together but pin 1 and 2 are marked as +EXV so while it's not clear exactly what is happening I it makes sense that the wiring harness had pin 1 and 3 connected to one another.

As already mentioned the I/O board also supports outputs which can be connected to CN3 so I connected up an LED via limiting resistor from pin 51 (output 1) to +5V and another LED from pin 52 (output 2) also to +5V. Using Virtua Tennis I entered the game's test menu and went to the output test option and found that I could get the LED's to light in different patterns. When playing the game I saw that the output LED would light and go off whenever a point was won unless it was the match point.

Use Dreamcast Arcade Stick on NAOMI

Unless you have a cabinet for your NAOMI it can be difficult to find space for the various parts of a NAOMI system and you'll need to connect up some form of input, as already mentioned. An arcade stick is quite fitting, especially the official Dreamcast arcade stick as it is a decent fighting stick with a good number of buttons, is a reminder of the NAOMI's Dreamcast roots, and can just about house a NAOMI board. By taking advantage of the fact that the arcade stick would normally draw power from the Dreamcast we can keep the arcade stick's original cable and have it power the NAOMI I/O board. In fact, one of the goals of this project is to ensure that the Dreamcast arcade stick is not modified in any way that it could not be returned to being a Dreamcast arcade stick. This project will work with both the original NAOMI and the NAOMI 2.

For the complete wiring diagram please see as follows:

The NAOMI is normally connected to an I/O board using USB connectors and cable but the actual wiring and protocol is not actually USB which means that no power is transmitted across the USB cable. A NAOMI I/O board, such as the 837-13551 which is used in this project, only needs 5V to power it if using inputs only, and it would normally get power from the NAOMI wiring loom. What we can do instead is provide 5V through the Dreamcast arcade stick cable, either from the NAOMI PSU or from CN12 on the NAOMI. I used a Dreamcast controller extension cable, which I cut one end off, and then soldered a USB cable (with one end cut off) with USB type-A plug and a wire with female connector on one end for 5V.

In the photo below you can see the USB lead plugged into the NAOMI (2) and the yellow wire on the right carrying 5V, with both leads merging into the Dreamcast controller extension cable (off camera).

I removed the PCB from inside the Dreamcast arcade stick and soldered a cable to mimic what we have on the NAOMI end and mate with the internal arcade stick lead connector: a USB cable with type-B connector to plug into the I/O board and wire to carry 5V with female connector for CN7 on the I/O board. Since we have a common GND both on the I/O board and the NAOMI there is no need to duplicate the GND connection to CN7 on the I/O board or CN12 (or the PSU) on the NAOMI. I have, however, purposely not mentioned any wire colours as they can vary between USB cables and instead have provided the USB pin numbers of the cable connectors on the NAOMI and I/O board side. Make sure that the USB connections of the cable to be plugged into the NAOMI match the USB connections of the cable to be plugged into the I/O board before powering up the NAOMI.

The buttons of the Dreamcast arcade stick are separated into 2 groups with their own connectors; the stick direction buttons, and the start and trigger buttons. The numbering of the button connections refer to the numbering used on the arcade stick PCB (where there is no numbering pin 1 is designated with a square solder joint). Both groups have their own common GND connections and all we have to do is make up 2 cables to mate with the button connectors and the I/O board CN3. I didn't have a spare connector to interface with CN3 and I didn't want to cut up a NAOMI loom so I just used individual jumper wires that have a female connector on one end.

There are a few loose ends; pin 1 and 3 of CN3 on the I/O board must be connected together for the I/O board to work, and to trick the NAOMI into thinking that coin meters are present 2 resistors are used, 1 between pin 2 and 49 of CN3, and the other between 4 and 50 (both player coin meters are taken care of even though we are only using 1P controls).

In the below photo you can see the underside of the Dreamcast arcade stick metal bottom plate removed, showing the upside down NAOMI I/O board ( I did try a smaller I/O board but that had even more trouble fitting as it had too many components packed close together which go in the way of the arcade stick plastic post. You must place an insulating layer (paper or card) between the metal plate and the bottom of the I/O board to prevent shorting and to lower the chance of components being physically damaged.

You can see the USB cable and yellow lead at the left of the photo which merge into a mating connector for the internal connector of the arcade stick lead (it could do with being held down better). At the bottom right you can see one of the 'coin meter' resistors which I have protected in heat shrink.

When you are sure everything has been connected up correctly power up the NAOMI and although you won't see the lights on the I/O board now inside the arcade stick you should hear the relay click. As soon as you can enter the test menu and select JVS test to check that the I/O board has been detected. If it has you can go to the Input test option and confirm that pressing buttons on the arcade stick show up and you can also further test using a game's I/O test option as well as, of course, by playing the game. I used what I thought was logical mapping having A, B, C, X, Y, and Z map to 1P SW1, 1P SW2, 1P SW3, 1P SW4, 1P SW5 and 1P SW6 respectively.

You can view a video I did about this project at:

https://youtu.be/AZUpZCrzK_o

NAOMI Cartridge Teardown

NAOMI cartridges are a lot more complicated and higher capacity than cartridges used with game consoles of the day as we shall see shortly. First, take a look at NAOMI cartridge (Virtua Tennis/Power Smash):

The NAOMI cartridges only have a top cover held in by 2 screws on the underside since the intention is to have the cart installed in the NAOMI for an extended amount of time which would protect the bottom of the cart.

Next let's take a gander at the internals of the Virtua Tennis cart starting with the top board. Note that I referenced the MAME source code to confirm some of my findings:

https://github.com/mamedev/mame/blob/master/src/mame/drivers/naomi.cpp

This is what the top board looks like:

The interesting components are:

JP1 jumper in position 1-2, to set size of EPROM. Position 1-2: 32Mb. Position 2-3: 16Mb. When in position 1-2 it routes A20 of IC22 (EPROM) to somewhere else on the board, allowing for the full address space of the ROM to be accessible.

CN1-CN3 interface with the NAOMI (bottom side). It seems these connectors are always in pairs (male and female).

CN4, unpopulated.

OSC1 TXC-2H 28.000 28MHZ crystal oscillator.

IC1 to IC11, Sega MPR-22916 to Sega MPR-22926 mask ROMs.

IC22 EPR 22927 M27C322 32Mb EPROM.

IC23 to IC25 74F245 Octal Bidirectional Transceiver with 3-STATE outputs.

IC27 to IC32 74F245IC36 74F157A Quad 2-Input Multiplexer.

IC37 X76F100 1Kb Secure Serialflash.

IC41 Xilinx XC9536 In-system programmable CPLD.

IC42 Sega 315-5881 317-0263-COM Unknown. 'COM' indicates will run with any BIOS, 'JPN' requires Japanese BIOS.

IC44 to IC45 71256SA 256Kb SRAM.

IC47 74FCT16245 16-BIT bidirectional transceiver.

The bottom board is as follows:

The board is marked as Sega 171-7919A which is the type of board (Mask ROM). The ICs on this side have an 'S' suffix which are listed below:

IC24S 74F245 Octal Bidirectional Transceiver with 3-STATE outputs.

IC26S 74F245.

IC33S to IC35S 74F138 1-of-8 Decoder/Demultiplexer.

IC38S to IC40S 74FCT16373.

IC43S 74F245.

IC46S 74FCT16373 16-Bit Latches.

IC12S to IC21 unpopulated (mask ROMs).

NAOMI NetDIMM Teardown

The NetDIMM can be used with the GD-ROM unit or for receiving games over a network and acts somewhat like a cartridge as far as the NAOMI is concerned. Here is what a NetDIMM looks like:

At the very left is a compartment that houses the backup battery (not screwed down but instead must be prised open) and to the right you can see an opening in the metal cover that exposes the security 'key' chip. Above the opening is a sticker indicating the firmware version and to the very right is another sticker but this one specifies the main RAM size that the game gets loaded into. At the front left is the serial interface to get debugging information, to the right of that is the ethernet socket for connecting to a network, and at the very right is the SCSI connector for interfacing to the GD-ROM unit.

To disassemble the NetDIMM remove all the screws, take out the metal plate. and then lift the small board off the main board and out of the case which will free the main board for removal.

There are 2 boards that make up a NetDIMM as can be seen below:

Now for some information about the boards, starting with the smaller add-on board:

Top side: labelled Sega 2001 837-14226-01.

CN3 ethernet connector.

CN4 SCSI connector.

CN6 Serial connector.

CN5, CN7 and CN8 unpopulated connectors.

LED1 to LED4 status LEDs, not normally visible.

LED5 unpopulated.

JP1 to JP3. Select netBoot (JP1 and JP2 1-2, JP3 2-3)/GD-ROM boot (JP1 and JP2 2-3, JP3 1-2).

JP4 to JP6

JP7 unpopulated.

IC1 PCnet AM79C973 10/100Mbps PCI ethernet controller.

IC2 831XX 1K EEPROM.

IC3 TDK TLA-6T121 pulse transformer.

IC5 PIC16F628A (8-bit microcontroller) security key.

IC6 socket but no chip, marked as 'ACE'.

IC9 ADM3222 line driver/receiver.

IC11 315-6334

IC4 Altera flex EPF10K30EQC208 PLD.

Various other unpopulated components.

Bottom side: labelled Sega 2001 171-8180B.

Note: components on underside have 'S' suffix.

CN1S and CN2S interface with main board.

Next, the larger, main board:

Top side: labelled Sega 2000 837-13987-04

Various test points.

SW1 unpopulated but marked as reset.

LED13 to LED16 (in pairs opposite sides of the board) not normally visible, possibly status lights.

CN1 to CN3 interface with NAOMI system.

CN4 unknown use.

CN8 unpopulated.

CN9 battery connector.

CN10 to CN11 interface with smaller board.

JP2.

JP3 to JP5.

IC1 unknown (hidden by heatsink).

IC2 315-6154 SH-4 CPU to PCI bridge and SDRAM controller according to MAME source code.

IC3 unknown (hidden by heatsink).

IC8 Sharp 070XZ1H Low voltage voltage regulator.

IC10 HY57V65322 4 banks x 512K x 32Bit SDRAM.

IC16 CY2306SC unknown.

OSC1 66.6666 66.6666MHz oscillator?

IC17 CY2309 zero delay buffer.

IC18, IC19, IC22, IC23, IC32 3771 0319 369 Unknown.

IC20 LVC04A hex inverters.

IC21 LVC08A quad 2-input AND gates.

IC34 HY57V161610 2 banks x 512K x 16-bit SDRAM.

IC36 M29W160ET 16Mb flash memory.

CN5 to CN6 RAM holders. MT16LSDT6464AG-13ED2 512MB 133MHz installed in CN5.

Bottom side. Has a sticker: WindRiver VxWorks (handled the OS used by the board).

IC6S B27AB marked as MM93C46A on the board. Unknown.

IC31S CY2308 zero delay buffer.

IC11S HY57V653220 4 banks x 512K x 32-bit SDRAM.

IC12S LCX16245 low voltage 16-bit bidirectional transceiver.

IC25S LVC32A quad 2-input OR gates.

IC28S M25AC2653 unknown.

IC27S 316 1433B unknown.

IC26S 3800 0303 324 unknown.

IC35S HY57V161610 2 banks x 512K x 16-bit SDRAM.

NAOMI Troubleshooting and Tips

Test your NAOMI is working correctly by using the test mode (system menu) by pressing the test switch. As you can see below there are options to test the NAOMI's RAM, inputs (JVS test), sound and so on:

Each game has its own test options; enter test mode while the game is running and then select Game test mode. Typically there will be options to test input, output, sound, etc.

Games can be set to free play so there is no need to simulate inserting a coin. While the game is running enter test mode, select the coin assignments option and keep cycling through until you reach the free play option.

If you cannot get a DIMM, NetDIMM board or game cartridge to be detected by the NAOMI or you get error 01 try disassembling it and putting the board (with the daughter board attached if applicable) directly into the Naomi.

It is not necessary to have a game or DIMM/NetDIMM board inserted into the NAOMI for it to boot.

It can take almost 40 seconds for a NAOMI to show any signs of life so be patient when the system boots.

If you are trying to use a TV with the NAOMI via VGA and it will not latch onto the signal try a monitor, or a VGA to HDMI adapter with the TV.

After changing network settings you must power off the NAOMI and back on for it to use the new settings.

A NetDIMM can only be set to load games from either a network connection or GD-ROM so make sure you enable the correct option using the jumper settings of the NetDIMM.

If the NetDIMM is not retaining a loaded game after power off and on again then possibly the battery has expired which will need to be replaced.

A NetDIMM has built-in LEDs on both boards not normally visible unless the cover is removed and are useful for checking that the NetDIMM is functioning correctly.

If you power on a NAOMI with a NetDIMM attached and you get error 31 it may be that the memory has been corrupted due to the NetDIMM backup battery dying.

The Japanese BIOS for the NAOMI is the best version to have as it has the most compatibility with games, however, games will display Japanese text (there may be an option to change the language).

Although you can easily upgrade a NetDIMM's memory beyond 256MB, no NAOMI games should require anything more than 256MB.

You may be tempted to power a NAOMI from a PC ATX power supply but it isn't a good idea as a NAOMI can easily be damaged by even a slightly too high voltage (e.g. 5.2V on the 5V line); it's best to use a power supply that was designed for the NAOMI.

For help with wiring a NAOMI you can have a look at the service manuals (not all of them have wiring diagrams though). Just search Google for the game name such as Jambo! safari pdf.

NAOMI error codes:

https://wiki.arcadeotaku.com/w/Sega_NAOMI_Error_Codes

Sega NAOMI 2 Introduction

The original NAOMI was followed up with an improved version in 2000 and is fully backward compatible with the first NAOMI which is just as well as the NAOMI 2 had fewer games released for it compared to the first NAOMI. The NAOMI 2 has 2 CPUs (x2 Hitachi SH-4 CPU running at 200MHz), improved graphics capabilities (x2 PowerVR 2) and more video memory (32MB). The NAOMI 2 would be Sega's last arcade system of its own making as subsequent arcade boards would be based on non-Sega consoles (e.g. Triforce) and PC hardware (e.g. Lindbergh).

Let's take a look at a NAOMI 2 from the top:

Games

Like with the first NAOMI, the games released for the NAOMI 2 came on both cartridge and GD-ROM with games including Virtua Fighter 4, Virtua Striker 3, King of Route 66, Beach Spikers and Wild Riders; a number of these games were ported to the PS2 and GameCube. A number of games for the NAOMI 2 made use of a card reader with examples being Initial D and Virtua Fighter 4.

The following screenshots are from Beach Spikers and Virtua Fighter 4:

All content of this and related pages is copyright (c) James S. 2019