Wheel Mouse Support Under IRIX
Here's a great tip if you're wanting a little more flexibility with your input devices under IRIX.
If you are running IRIX 6.5.16 or newer on a system that has a PS/2-style mouse port, you can enable support for PS/2-style mice that have more than three buttons, including mice with scroll wheels.
Supported systems include SGI Indy, SGI Indigo2, SGI O2, SGI Octane, SGI Fuel, SGI Onyx2, SGI Onyx 300, SGI Onyx 3000, and SGI Tezro systems. Older systems, such as the 4D series, SGI Indigo, IRIS Crimson, and SGI Onyx, are not supported.
By default, IRIX only recognizes basic, non-scrolling, three-button mice. To activate support for additional buttons, including scroll wheels, you will need to use systune to set the pcmouse_mode kernel parameter to a value that is suitable for your mouse.
PC Mouse Mode Settings
Here are the possible systune settings for pcmouse_mode to use scrolling wheels in IRIX:
0 - Default 3-button mode
1 - 3-button Wheel Mouse (type 3), Wheel scrolling generates button events 4 & 5.
2 - 5-button Wheel Mouse (type 4), Wheel & buttons 4 & 5 generate button events 4 & 5.
Since I am using a Intellimouse Explorer, I chose '2'. The command to activate support in my case would then be (as root):
systune pcmouse_mode 2
After a reboot both the scroll wheel and middle button should be active. On a five button mouse such as the Intellimouse Explorer, the two additional buttons function as scroll up/down. You should also see an entry in /var/adm/SYSLOG like this:
Dec 15 20:19:07 5A:Mika unix: NOTICE: pcmouse: type=4
I've found the scroll wheel works wonderfully with Mozilla, SkipStone and many freeware applications available on http://freeware.sgi.com. If you use aterm as your default terminal it works with that as well.
Note: According to the man page for pcmouse, "SGI does not support running mice in enhanced mode when connected through a switch."