Hey all, long time no post, but I have a question I'm sure someone here could help me out with.

I'm building a MAME cabinet and I have a trackball and a DIY Spinner I'd like to install. Both are PS/2 mice. Can I somehow plug both in together? I know you can have two USB mice at once, but I've never tried PS/2 as there's only one PS/2 port on a computer.

Can I just splice the wires together? Or do I need some kind of special adapter?

(I don't need two cursors, both mice control the same cursor.)

welll the cheepy answer would be to use two ps2 to usb convertors witch come with most mice

See if either is compatible with either a passive (pin-only) PS/2 to USB (very few are) or PS/2 to Serial (common on older ball mice), then all you need is a really cheap adapter. Serial compatible mice may have a small switch on the bottom to switch between modes, but you're going to have to Google to see if a newer one is compatible with USB directly. I don't think you can Y them off the same port, but using serial or USB would work.

If neither has compatibility with passive adapters, you'll need a PS/2 mouse and keyboard converter (with circuitry inside). Here's a cheap one.

The trackball has a USB cable, as well as PS/2, but last time I tried it, it the computer didn't recognize it... I tried it yesterday and it works perfectly! Strange. But now I have a trackball and a spinner in my arcade control board and I couldn't be happier.

Thanks for the tips anyway!

I think you need a microcontroller to take 2 inputs off of 1 cable.

But like you said, it works...

Im not sure if I read it right, but this software lets mice become switched on the fply by simply taking control with the left mouse button. I've seen it in use, and it seems to be fairly stable and easy to use.
http://www.dicolab.com/