: I have one of these also. It's useful for debugging device drivers when
: printk's perturb the environment enough to make a bug disappear.
: All you need to do is output a value to port 0x80.
: However, the SLOW_DOWN_IO code in asm/io.h writes random values
: to port 0x80, which tends to obscure the values written by users.
There is also a hook in the keyboard driver that allows a driver
to take control of the keyboard leds, so that these continually
display three bits of information. Not much, but potentially useful.