I'm pretty sure if you installed multiple pointing devices they would just all fight for control of the pointer. On laptops you can have a pointing stick, touchpad and USB mouse all active and fighting for control. Whichever one you move/click will be active. You can move on the touchpad to the left and your mouse to the right, and the poor pointer will struggle with itself on the screen.
Little correction to the theme: PCs do have "dual input", but these inputs are used for the same operation (do the same command): (it's like digging the same ditch by the shovel or bare hands). PSs on the other hand have dual input which do different things at once (digging two different ditches..) Kapish?
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Depends on the software sometimes, as well. For instance, with the NHL series... one player could use the keyboard, and the other player could use the mouse, joystick/pad, or the other half of the keyboard. I've never tried using more than one mouse before... but I don't think it's possible.
<font color=red> If you design software that is fool-proof, only a fool will want to use it. </font color=red>
Back years ago when I had my beloved Amstrad CPC, you could plug two joysticks in (on the same port, incidentally). If you were at the "Ready" prompt, Joy0 would produce a certain set of characters when you moved it, and Joy1 would produce a different set of characters.
My guess is that the same basic principle was used on the CPC as is used on modern consoles, so that the input signals to the OS are different for each of the four joypads. Whereas if you had two mice, since Windows is only expecting one mouse, it only has one set of input signals assigned to the mouse.
Is there anybody hanging around here who can confirm or refute this?
By the way, for a while, I had two mice plugged in, both on mobo USB; my gaming mouse (a corded Logitech iFeel MouseMan) and a wireless MS Explorer-thang.
I noticed that my performance in games had taken a dramatic turn for the worse. I don't mean graphical performance, I mean how well I did in the game. After a little experimentation, I found that having both mice plugged in, even when the wireless one was inactive, I got vastly increased "mouse spaz". There was me thinking my hands were shaking (from too much coffee, most likely), but in fact it was my other mouse, arguing with the one I was using.
Dunno how relevant this is, but I just thought I'd share