I recently bought a ThinkPad L420 and decided to run Ubuntu on it. Unfortunately, it only works (i.e. boots) when booting with disabled ACPI. Otherwise, the boot process would just not finish. Of course this means HyperThreading is disabled and other stuff is not working (no suspend, hibernation, need to press the power button after shutdown etc). How do I get it resolved?
Updating to the newest BIOS (available as of now) should resolve the issue.If you are using a 64 bit version of Linux,it should recognize all of your RAM and all the CPU Cores as well.