Understanding the Differences of Jamma and JVS

Hey this is a rad test post but lets talk about the differences of JAMMA and JVS arcade system hardware.

When I first entered the scene of arcades I dove in head first but I remember being confused about JAMMA and especially JVS when I started. So this post is a little discussion blurb about these two standards.

In prior to around the mid to late 80s there was zero standards to arcade machines across manufactures. Different companies used different wiring and different games from the same companies sometimes used different wiring too.

JAMMA was created to solve a growing issue in the Arcade operator space at the time, new games were coming out more and more but they all used different wiring and standards. This meant operators had to strip an entire cabinet apart and upgrade the wiring or home brew an adapter if they wanted to convert their machine to the newest game title.

Enter the era of JAMMA, no longer did an operator have to worry if the new game coming out would work in their cabinet or not because it was standardized to just plug in and work.

So what is JAMMA really?

It was a scary thing to think about when I started the hobby? Not everyone here wants to become an electrical engineer just to play video games, however to enjoy arcade games you probably need to learn the ways of the arcade operator.

Fear not because its quite simple. JAMMA in the most general way to explain it is quite literally the equivalent to a cartridge slot on a Nintendo. Plug game in and game play comes out. It is quite literally the arcade cabinets cartridge slot and in many cases its quite literally this easy.

Its simple its easy HOWEVER make sure you don’t plug it in upside down and make sure your power supply is okay otherwise your several hundred or several thousand dollar board might be blown up.

JAMMA standard asked that a cabinet provided controls, a speaker and a monitor. While the board was expected to provide a mono amplifer, 15khz RGB video output.

Stereo sound output was not part of the JAMMA standard and so the setups for stereo depends greatly on the game board, if it was even offered at all.
Boards that offer stereo sound often have some selection switch on the board and a connector to connect up to stereo speakers on the cabinet.

It can be a little more deep than this if you wanted to get technical.
The likes of MVS having its own modified version of JAMMA for multi-slot motherboards (you know to add stereo and the game select button), and the later JAMMA+ addition in the 90s.

However its all designed around one 56 pin wiring connector and its designed to be more or less idiot proof and fast.

You can see in the above photos the JAMMA edge connector and then a NeoGeo MVS 1 slot system board being plugged into it to play KOF.

Note: Since this is a single slot MVS system it retains the standard JAMMA pin-out.
A common misconception is that MVS multi slots cannot run on standard JAMMA and while this is more or less something you would not want to do, it will not blow up or damage your MVS multi slot board.

What about fighting games? I need 6 buttons?!!

JAMMA actually predates the explosive era of fighting games. Many games only used 3 buttons and the standard allowed expansion for 4 to sometimes 5 buttons if you added them but not 6 buttons.

Because fighting games needed 6 buttons manufacturers created something called the Kick Harness. Its for your kicks.

The kick harness has no real standard different boards used different kick harness’s but manufacturers generally tried to standardize the kick connection they used.

Capcom for example is well known for the CPS1 and CPS2 system boards. Those system boards used two different connectors, CPS1 kick harness and CPS2 kick harness.
Actually the CPS3 system also used a CPS2 kick connector, I guess they got tired of changing the connector.

The hobby scene tends to stick to CPS2 kick harness connectors for most kick harness needs.

Okay so what about JVS?

So whats this JVS business whats it all about?

JVS is the JAMMA Video Standard, great acronym I know.

JVS was created to try to steer standardization into the “modern” age of arcades. An era where game hardware was increasingly more power hungry and video output needed to be VGA 31khz 480P output not just simple RGB. Control interfaces were adopting digital and the future was on its way Y2K baby!

To explain JVS in the most simple way possible it is like your desktop computer but the power supply is not inside the computer case. Everything has been broken out into its core functions. In-fact later JVS systems are quite literally a computer (but they put the power supply inside the computer case … haha sorry).

JVS systems have some kind of hardware system, like a Naomi for example, everything is broken out more than JAMMA. You have a system board, a JVS compliant power supply for boards that need it, a stereo amplifier, and a IO board which took care of controls.

These 4 key parts make up a JVS machine at its operational level. The cabinet was expected to provide everything a JVS system board needed to run, then if the system board needs to be upgraded to the next best hardware everything else stays but the system board upgrades.

If you look at the diagram above it may make more sense about this standard. Its at its basic form similar to JAMMA where you have a board that has the game and it plugs into a cabinet that can run the hard ware. In this case a JVS compliant cabinet.

The key difference with JVS compared to JAMMA was that it allowed a lot more flexibility while also adopting the use of digital IO boards which was very helpful in trying to standardize edge case hardware like analog inputs or dedicated arcade machine setups while also maintaining standardization in the multi game cabinet market (aka candy cabs).

Many people also like to explore JVS to JAMMA conversion (seen above).
This topic is a little more advanced and was what tripped me up the most.

The board pictured above is a Sega 838-13683-02 and its the zero thrills work horse converter Sega put out. Its job was very simple. Convert JVS digital controls and VGA 15khz video to JAMMA controls and raw RGB. It also handles Analog input/outputs and some extra button input outputs and digital 7 segment LED boards that the Versus City used.

More feature rich converter however did basically everything for you. The Capcom JVS converter IO for example would provide power output conversion, stereo amp or mono JAMMA audio output, 6 button support over CPS2 connectors.

If you want to read up more on JVS and its different IO boards Arcade Otaku Wiki has tremendous information on tons of topics.

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