second core CPU power state depends on battery state at boot time

Binary package hint: linux-source-2.6.22

(using gutsy, but I think it was the same in feisty)

using a "Genuine Intel(R) CPU T2400 @ 1.83GHz"

if the computer was unplugged at boot time
 * both processors go to C3 when the laptop is unplugged. (1)
 * CPU0 goes to C2, CPU1 to C3 when the laptop is plugged in. (2)

whereas, if the computer was plugged at boot time
 * CPU0 goes to C3, CPU1 to C2 when the laptop is unplugged. (3)
 * both processors go to C2 when the laptop is plugged in. (4)

=> So it looks like CPU1 available powerstate are defined at boot time and never modified, whereas CPU0 changes when the laptop is plugged or unplugged.

---------
(1)
cat /proc/acpi/processor/CPU*/power
active state: C3
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
    C2: type[C2] promotion[C3] demotion[C1] latency[001] usage[00024024] duration[00000000000114130312]
   *C3: type[C3] promotion[--] demotion[C2] latency[057] usage[00112408] duration[00000000000645676141]
active state: C3
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
    C2: type[C2] promotion[C3] demotion[C1] latency[001] usage[00551884] duration[00000000002261918965]
   *C3: type[C3] promotion[--] demotion[C2] latency[057] usage[04377438] duration[00000000031179229264]

---------
(2)
 cat /proc/acpi/processor/CPU*/power
active state: C2
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
   *C2: type[C2] promotion[--] demotion[C1] latency[001] usage[00071033] duration[00000000000410369580]
active state: C3
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
    C2: type[C2] promotion[C3] demotion[C1] latency[001] usage[00565392] duration[00000000002326080358]
   *C3: type[C3] promotion[--] demotion[C2] latency[057] usage[04501678] duration[00000000031832189184]

---------
(3)
cat /proc/acpi/processor/CPU*/power
active state: C3
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
    C2: type[C2] promotion[C3] demotion[C1] latency[001] usage[00003896] duration[00000000000022791437]
   *C3: type[C3] promotion[--] demotion[C2] latency[057] usage[00024417] duration[00000000000235697781]
active state: C2
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
   *C2: type[C2] promotion[--] demotion[C1] latency[001] usage[00112419] duration[00000000001047405218]

---------
(4)
cat /proc/acpi/processor/CPU*/power
active state: C2
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
   *C2: type[C2] promotion[--] demotion[C1] latency[001] usage[00072639] duration[00000000000618470508]
active state: C2
max_cstate: C8
bus master activity: 00000000
maximum allowed latency: 8000 usec
states:
    C1: type[C1] promotion[C2] demotion[--] latency[001] usage[00000010] duration[00000000000000000000]
   *C2: type[C2] promotion[--] demotion[C1] latency[001] usage[00070689] duration[00000000000656339622]