Comment 141 for bug 578673

Radko, your feedback is very appreciated. For 2.6.35 and older kernels you need to apply acpi_sleep option into GRUB like this:

1) $ sudo nano /etc/default/grub
2) Search for GRUB_CMDLINE_LINUX="" and make it look like GRUB_CMDLINE_LINUX="acpi_sleep=nonvs"
3) Save and run: $ sudo update-grub2
4) reboot

(instructions above are valid for GRUB 2 which comes by default since Lucid i believe)

With 2.6.36 kernels GRUB editing is no longer necessary.
Expected result: always resumes on AC; almost always fails on battery-power; always resumes on both AC and batteries with SpeedStep disabled in BIOS. Disabling SpeedStep (CPU Frequency Scaling) by other methods like forcing CPU governor to performance or unloading cpufreq module (which is not possible on standard recent kernels, because it is no more a separately loadable module) does not have the same effect like disabling SpeedStep in BIOS.