NEW QUESTION
Keywiz or Ipac?
Well.. to me... it comes down to... how cheap are you (and are you handy with soldering iron) AND are you going to be buying other stuff from ultimarc anyways therefore the "extra" savings from domestic shipping (assuming US resident) is nullified...
I use a key wiz and am happy with it... but if I was going to be ordering j-sticks/Avga card/etc etc and need a keyboard encoder I'd bundle in the ipac at the same time...
*shrug*
YMMV,
rampy
Soldering iron not required unless you go with the KeyWiz Eco model. The KeyWiz Standard is still less expensive than the I-Pac and has screw terminals.
In response to the initial question - USB is limited to about 14 or 16 simultaneous inputs, PS/2 is unlimited. More than enough, but. . . I also have heard of people having problems with the I-Pac in USB mode and never in PS/2, FWIW.
Multiple trackballs/spinnners - tons if you count two or 3 player driving games, plus Marble Madness, CABAL, Rampart, Blasteroids, Atari Football, Atari Soccer, Warlords (4), . . . tons . . .
Regarding KeyWiz vs. I-PAC, the main issue is do you need a Keyboard pass-thru or want keyboard LED's on your CP. If so, go with the I-Pac. If not, the KeyWiz offers 4 more inputs at a lower cost (assuming domestic shipping in the U.S.)
Other differences - I slightly prefer the KeyWiz software, but either one is easy to use and easy to program. KeyWiz is smaller, if space is an issue. Shift key functionality is different between them. Overall, I think the KeyWiz has a better implementation of this feature, but I don't care much for shift keys anyway.
KeyWiz uses SDRAM. I-PAC uses EEPROM. SDRAM is infinitely re-writeable, whereas EEPROM is limited to something like 100,000 or 1,000,000 writes (I've seen both numbers quoted). So if you load 10 code sets a day, your I-PAC may wear out in 10 years, while your KeyWiz will still be going strong. Seriously, though, what this means is this - KeyWiz does not store alternate settings in memory - so if you want to use a different set of codes than the default, with the KeyWiz, you have to load the different set each time you start the cab (from the autoexec.bat). With the I-PAC, you just re-program the EEPROM and you're done. OTOH, if you use games and emulators other than MAME on your cab, the KeyWiz will load alternate codesets faster than the I-PAC (at least in theory).
Also, I would consider multiple OSCAR $9 USB interfaces over the opti-pac, but that's kindof a toss-up. The KeyWiz does have a +5V output, so you can hook an Opti-pac to it. (And the USB opti-pac may not need an external +5V.