In case anyone else has this issue, I found that my 7 year old Dell Latitude D830 laptop was choosing to reduce the CPU speed to 800 MHz (rather than keeping it at 2.4GHz when KStars needed it). I can only think this was due to processor temperature but it was only in the low 60's C so I:
- Installed a more configurable fan driver
- Gave myself control of the CPU speed as follows:
apt-get install cpufreqd
Edit the configuration file /etc/cpufreqd.conf to make sure that the CPUs remain in high performance mode for the temperature range I normally expect (I chose up to 65 C). I also added kstars as a program that would trigger high performance mode.
To make this work I also needed to edit /etc/modules to add the following modules to the list:
acpi-cpufreq
cpufreq_ondemand
cpufreq_userspace
cpufreq_conservative
cpufreq_powersave
...and [carefully!] edit the boot file /etc/default/grub to disable the Intel power-state driver. Look for the line beginning with GRUB_CMDLINE_LINUX_DEFAULT. At the end of the line add intel_pstate=disable, so it becomes:
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash intel_pstate=disable"
Then enter:
sudo update-grub
...then reboot.
Now I can make the fan work when I want it to and make the CPU give me the performance I need. Oh, and I also made sure the fan exits on the laptop were nice and clear.
Rob