I still had one other nagging problem trying to run the latest version of CentOS Linux on my Dell Inspiron 8100, which includes a Pentium III Mobile CPU capable of SpeedStep. The keyboard and mouse were very jerky. In fact, I would lose actual keystrokes. It's very annoying to type a sentence and lose half of the words. Even very old computers usually do not lose keystrokes, and although they might lag behind a bit, the keystrokes eventually come out of the input buffer. This was a real problem for me since I am a reasonably fast typist.

The issue occured whether or not I was connected to power or running off the battery.

I tried a number of suggestions (such as disabling ACPI by specifying a boot time kernel option) but nothing seemed to work.

Finally, with CentOS 5 installed, I found the solution... turn off the actual daemon that attempts to throttle the CPU speed.

# service cpuspeed stop
# chkconfig cpuspeed off

I'm sure this will affect my battery life, but this laptop doesn't get particularly good battery life anyway and I am usually plugged into a wall outlet. It is possible that the cpuspeed config file (/etc/sysconfig/cpuspeed) could be tweaked to solve the input problem but I did not bother researching this further.