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Ultimarc's Mini-Pac

Integrated Switch/Joystick/Trackball/Spinner Interface with Wiring Harness


This Mini-PAC is a unique product as it is a 2 player keyboard encoder, trackball/spinner interface, and control panel wiring solution all in one. You can think of it as a merged I-PAC 2 and Opti-PAC with a convenient wiring harness.

First I want to say up front that I am biased towards Ultimarc’s products, I have had an I-PAC 2 and Opti-PAC in my upright MAME cabinet for years. The other main reason I prefer Ultimarc is because of Andy himself. He has always gone out of his way to address any questions or issues I’ve had quickly. Even if I was trying to do something with one of his products that it really wasn’t designed for, Andy would give me all the help and info he could. I’m not saying that there aren’t other good vendors out there as well, just that I’ve had very good support with Ultimarc. At the same time, I am picky about hardware. I’ve tested the Mini-PAC every way I could think of so I think I’ve got all the bases covered.


The Mini-PAC at a glance:

  • Keyboard encoder with 28 direct inputs (PS/2 or USB)
  • Optical interface for trackball and spinner (USB Only)
  • Wiring harnesses available for header style wiring connector
  • NVRAM memory
  • Shift and macro function support
  • Programming utilities for Windows, Macintosh, Linux, and DOS
  • PS/2 keyboard pass-through port (even works in USB mode)
  • Diagnostic LED
  • Can drive CAPS/NUM/SCROLL LED’s
  • Can program using keyboard without programming utility


First Impressions

When I received the board I was stunned at how compact it is. I was used to my I-PAC 2 and Opti-PAC which are about 4 times bigger each. The kit I received contained the Mini-PAC board, a wiring harness for joysticks/buttons/spinner/trackball, a wire harness extension kit, and a PS/2 to USB cable. Fortunately I already had a PS/2 to PS/2 cable from my I-PAC 2 that I could use to test the board in PS/2 mode as well. The board I received is newer than the one pictured on Ultimarc’s website as the one I have has no jumpers. Ultimarc always includes their latest CD; it contains programming utilities and PDF documents from their website.

I am very happy that Ultimarc decided to keep NVRAM in the Mini-PAC. It seems like many newly released encoders lately lack this feature. Perhaps I think more of NVRAM than I should, but I love being able to set a configuration and have it stay. People who don’t think NVRAM is important usually suggest that you can easily program a board when the operating system starts, but that is an extra thing to configure and wait for.




It has two PS/2 style ports as well as a 40-pin and 10-pin header style connector. One PS/2 port goes to the PC either via a PS/2 to PS/2 cable for PS/2 mode, or a PS/2 to USB cable for USB mode. It is important to note that the trackball/spinner part of the interface only works in USB mode. The other PS/2 port is for cascading an external PS/2 keyboard or another keyboard encoder.


The 40-pin header is the main header as it has virtually all the important connections on it except 5v. If you are frugal you can purchase the board without the wiring harness and hack up an IDE cable for your wiring. When I first saw the Mini-PAC I thought that hacking an IDE cable would be the way I’d go, but the wiring harness is so nice that I would pay the price difference and save myself the work. The only way I’d go the IDE hack route would be if the harness didn’t fit the project’s needs for some reason. The wiring harness I received has 320mm long wires on it, so if you put the Mini-PAC in the middle of a CP, you could get a span of 640mm. Ultimarc is now shipping a longer harness that is 340mm, so you can have a span of 680mm with it. You can also buy an extension kit which offers 10 longer wires (580mm) you can swap for some of the original harness wires to reach far away controls.

There is also a 10-pin header which has 2 purposes. Its first purpose is that it has 3 pins providing 5v and 2 pins providing ground that the wiring harness uses for the trackball/spinner. This header was also designed to be pin compatible with the original 10-pin header on the I-PAC 2. So, you can use it to provide electricity to the trackball/spinner and also still drive LED’s for Caps Lock, Num Lock, and Scroll Lock if you need to.



If you want to use the full functionality of the Mini-PAC you will want to use it in USB mode. Even though the Mini-PAC works in either mode depending on the cable, the trackball/spinner only works in USB mode.

When I plugged it in for the first time, Windows XP recognized the Mini-PAC and quickly installed it without prompting for any drivers. I think any operating system that supports USB human interface drivers will do the same.

Programming is extremely fast and trouble free in USB mode, there is no waiting. This is quite a contrast from PS/2 programming where programming takes longer. The Windows programming utility is easy to use and works great. I especially like that you can tailor it to your actual control panel.

The one downside to USB is that there is a limit on the number of keys that can be pressed at the same time. You can have 10 regular keys and 6 special keys (left or right Ctrl, left or right Alt, and left or right Shift). That is a total of 16 concurrent keys for USB mode. This isn’t a big issue because the Mini-PAC is designed for 2 player panels—even with 16 concurrent keys you can have two players each with an 8-way stick use up to 6 of their buttons and joystick diagonals at the same time. Also, keep in mind that there is also a left and right mouse button you can use for 2 additional inputs as well. This is probably only a concern if you are going to try and use a Mini-PAC in USB mode with 3 or more players. PS/2 mode does not have this limitation, but if you use PS/2 mode you won’t be able to use a trackball/spinner.

Once I attached the wiring harnesses, I was ready to hook up some controls. I have a test control panel with an 8 way stick and 10 buttons so I began to hook them up. The ground wire is a single wiring coming off the harness and it hooks to a long ground wire which has connectors every 5 inches. Basically you just daisy chain the ground wire to all the controls common connector. When I built my original MAME cabinet, I spent hours and hours cutting, stripping, and crimping connectors. If this type of harness was available then I would have saved not only a ton of time but also the expense of wire, tools, quick disconnects, and molex connectors.


The painful wiring I could have been saved from:

I used the Passmark KeyboardTest utility to check that all the controls were reporting correctly. I played a couple games of my usual test game Asteroids Deluxe and it worked great. It didn’t take long for me to be defeated, as usual…

I then decided to move on and test the trackball/spinner functionality. As luck would have it, the harness I have is already configured for the trackball and spinner I’m using (an older Ultimarc 2.25”) and my spinner (Oscar Vortex). It took me a few minutes to identify which of the 3 connectors was the trackball X, trackball Y, and spinner. It would be nice if Ultimarc would label these in the future. Depending on your configuration and what harness you ordered, you may have to swap some of the trackball/spinner wires around in their connectors. I’ve not heard of anyone frying anything by hooking their spinner or trackball wrong, but since you’ve got 5v and ground as two of the connections, I would be sure you are hooking the wires up correctly before powering it on. The Mini-PAC only supports active low type devices, unlike the Opti-PAC which has the option of active low or active high. This really isn’t an issue because almost all devices are active low. The only devices that are mentioned on Andy’s website as active high are some Suzo trackball models.

As expected the trackball and spinner will lock each other out. This means that if you use the trackball, the spinner will not function until you stop using both controls for 5 seconds. If you stop using both of them, wait 5 seconds, and then use one, it will become the active control and the other won’t work until you stop and wait again. This wasn’t a surprise to me as the Opti-PAC works the same way. The idea here is that you don’t want to have the other control accidentally affect game play if bumped into.

The version of MAME I used for testing (0.106) can handle multiple mouse devices. I did the testing on my notebook which has an internal trackpad, so the Mini-PAC became the second mouse in the system. I had to tell MAME I wanted to use the second mouse for player 1 which just took going into the configuration menu and changing it. I fared a bit better at Tempest than Asteroids Deluxe! I also tried Missle Command and some Quantum with the trackball and both played great as well.

I hooked up my old I-PAC 2 PS/2 to PS/2 cable and power up the Mini-PAC in PS/2 mode. As mentioned above the trackball/spinner do not work in this mode, but the keyboard encoder works perfectly as expected. It does not have a limit on the number of concurrent keys. I think it is great that the Mini-PAC supports PS/2 mode as well because it adds flexibility.

PS/2 keyboard passthrough is implemented very well, and my attempts at mashing the keyboard were no problem for the Mini-PAC. All keys typed on the passthrough keyboard were reported quickly just as if it were the primary keyboard. This may seem like an easy thing, but other vendors have either not attempted it or had an unstable PS/2 keyboard passthrough. The Mini-PAC actually translates the PS/2 protocol to USB if you are using the Mini-PAC in USB mode!

Shift and macro support. Shift support is something I could not live without in an encoder. Here is a quick explanation of how the shift feature works in case you aren’t familiar with it. If you press 5 on a regular keyboard, then it types a 5. If you press Shift-5 on a regular keyboard, then it types a %. Think of that same concept on your control panel except that it is fully customizable. If you don’t have a shift feature, you would have to buy buttons, drill holes, wire extra controls, and have enough inputs for administrative things like insert coin, exit game, pause, etc. With the shift feature, you can pick a button that doubles as a button (Default is Start 1) and also as your shift key. If you press and release Start 1, it will send what Start 1 is configured to send. But, if you hold Start 1 down (like a shift key) and then press another key, you can have it send something completely different than if you had pressed that button without the shift. This technique can almost double the amount of keys your control panel can send. It also makes the control panel less cluttered. While I have never used the macro support, it is a great feature to have. It would be very handy if you are working with some software or emulator that requires multiple keystrokes to do something.



The Mini-PAC is currently offered in 5 configurations:


Included Harness
Included Interface Cable
Item Price
Shipped Price


You can always purchase the opposite interface cable later if you need to change the interface you want to use.

The optical harness is available in a Happ trackball version and also an Ultimarc trackball version. Don’t sweat it if you order the wrong one because you can easily turn one harness into the other one by swapping a few pins on the trackball connectors.

Andy said that Ultimarc’s original intention was to have two board versions, one that supports optical controls and one that does not, but at the time of this review there is only one board type which supports all controls. This is not guaranteed to be the case in the future because they intend on creating two board versions as time permits. For now however, this means that the Mini-PAC is an incredible value if you are on a strict budget and simply can’t afford more than the non-harness board only version. Trust me though, I’ve done some IDE cable hacking, and if you can afford it, the wiring harness is so much better and well worth the money.



The fact that the Mini-PAC has both keyboard encoder and an optical interface is very cool. I will admit that I didn’t see the advantage of the wiring harness until I actually had it in my hands. It was incredibly easy to work with. I can also appreciate that the Mini-PAC contains nearly full functionallity to the I-PAC 2 and Opti-PAC. The really great thing about the Mini-PAC is that it is an all in one solution that can take care of most control panels all by itself. It is a RetroBlast! recommended purchase.



  • Keyboard encoder AND optical interface
  • Available wiring harness saves time
  • Wide operating system and program utility support (Windows, Macintosh, Linux, and DOS)
  • NVRAM memory
  • No matrix
  • PS/2 passthrough that actually works


  • 16 concurrent key limit in USB mode (18 if you include mouse buttons)
  • Trackball/Spinner does not work in PS/2 mode

Order the Ultimarc Mini-Pac

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