Description of problem: See bug #188453. The problem is identical and the AC/battery behaviour too. I'm seeing this on a Siemens Lifebook E8010 running Cen^wRHEL 4.3, kernel -34.0.2.EL. Refiling as a separate bug since it's another distribution and a different package.
Still an issue w/the 4.4 and/or forthcoming 4.5 kernels? (I'm going to guess yes...)
RIP E8010. Three months ago I stupidly left it on the bed, fluffy isolating duvet under it, running. When I came back it was stone dead, presumably due to overheating related to this bug. I'm now using a Siemens Amilo Pro V2010, Celeron-M, on U4. On this machine there is no difference between AC and battery. Speed scaling doesn't work, period. For a couple of weeks now I've been meaning to install tikanga on this machine. If I do I can report on that, but then no onger on U5. What's more interesting for you?
RHEL5 is far more interesting to me, and quite a bit has improved wrt laptops and power managment between RHEL4 and RHEL5. If we can't get it working under RHEL5, chances are its a BIOS support issue.
Please open a new bug if there are freq scaling issues on the new machine, closing this one out due to the original machine no longer being available for test.