Ubuntu :: ACPI Thermal Zone Configuration

I originally installed Kubuntu 7.10 on an ACER laptop (exact model escapes me at the moment) and subsequently upgraded to 9.10 and then to 10.04. Starting with 9.10, I had problems with the computer suddenly turning off in the middle of doing work. Eventually, I figured out that when this happened, the bottom panel had gotten quite warm so it probably a thermal control measure. Further, I discovered that I could prevent this by setting the power regulator to powersave, which effectively kept frequency scaling at 50% and under which I never had the computer suddenly turn, the only exceptions being when unplugged the computer and replugged it in and it would switch to dynamic power policy thus running at full power.

However, after "upgrading" to 10.04, I can't do anything to restrict frequency scaling. Whether I set the regulator to powersave, ondemand or anything, CPU frequency can go to full capacity until it heats the CPU to the critical trip point, invoking poweroff. Sometimes, this would happen just a few minutes after "acpi -t" reported 40C (is there some way to test the output from acpi, I've seen it report obviously wrong figures such as 0C when the room was considerably above freezing?). While trying to figure out what to do, I discovered the /proc/acpi/thermal directory and subsequently the /sys/dev/... directory.

I would like to know which directory I should focus on and what files in order to establish trip points and direct actions that will force the system to reduce heating so it won't reach critical. It's not like it's particularly compute intensive tasks triggering this. I have had it happen while running nothing more than the windowing system, system monitor, terminal and paging through a file with less. I have looked for documentation online but have not found anything that clearly explains what I need to do. The only parts I understand from what I've found are "[critical]: S5", "[active]", and "[passive]". The "[passive]" line included items like "tc=..." and "device=0x...", but I have no idea whatsoever what any of those settings do and the documents do absolutely nothing to explain them.

1) what file I need to edit, 2) what options I can set in the file, 3) what values those options can take and 4) what effects those values have on ACPI's behavior. Lastly, the default setting HAVE GOT TO BE CHANGED. Having poweroff as the first line of defense against overheating is simply UNACCEPTABLE. What would happen if this occurs during the middle of a system upgrade? I know at least enough to figure what needs to be done, even if I can't figure out how to do it. Many users can't even do that and I don't think they should have to. The installation process should automatically detect what methods of reducing thermal output available (reducing frequency scaling, throttling, fans) and set trip points that invoke them before reaching critical.