My processor speed drops to 800 Mhz when my Lenovo Thinkpad W541 is plugged into the OEM cable
Solution 1:
I had this problem with the W541 more than a year ago, and it came down to the machine perceiving that it was getting insufficient power, and throttling down the CPU as a result. In my case, when the OEM adapter was plugged in, the power-settings switched to "Airplane" mode, which is a severely reduced power plan. Check what power plan you're running under when you're in this 800Mhz reduced performance state. While the subject line is a different issue, this thread fundamentally describes the problem and the solution.
(If you check "Control Panel -> All -> Power Options -> Airplane -> Change plan settings -> Change advanced power settings -> Processor power management - Minimum processor state", you'll see that for Minimum processor state, both "on battery" and "plugged in" are set to 5%, which was the source of my problem.)
If that doesn't resolve the issue, others have found the following to resolve the throttled-CPU issue:
- Shutdown windows
- Disconnect Power plug.
- Take out battery
- Press Power button couple of times (laptop wont start as no battery or power but this would drain any remain charge inside mobo)
- Put battery back in and plug back power (Issue should be solved Now)