Ubuntu
linux-source-2.6.15 package

  1. Bug #55686
  2. Comment #1

Comment 1 for bug 55686

Revision history for this message
Bryan Quigley (bryanquigley) wrote :

Apologies if I got this wrong.

"I see only C0, C1, and C2. Why don't the other C-states show?

It's mostly a BIOS thing. Some BIOS hide C3/C4 when on AC power, and others show only C3 which is really a C4 underneath when on battery. Note that the 'max_cstate:C8' value in /proc/acpi/processor/*/power tells the maximum number of C-states the Linux kernel can handle, not the number of C-states implemented in your hardware."
-http://www.lesswatts.org/projects/powertop/faq.php