ThinkPad CPU runs at reduced maximum clock speed with no battery installed

[#1]

Newer ThinkPads make use of high performance CPUs that may require more power than what the 65W adapter can provide while also supporting USB, Optical and other attached devices, especially in  docked configurations.  To prevent the potential for sudden system shut down if the power demand exceeds what the adapter can supply, the maximum clock speed may be limited when the system is operated on the 65W AC adapter and no battery is installed.

The following ThinkPad systems may be affected by this symptom:

ThinkPad Edge 13", E30

ThinkPad Edge E120

ThinkPad Edge E320
ThinkPad L420

ThinkPad L520
ThinkPad R60, R60e, R61, R61e 

ThinkPad R400, R500, T400, T500 
ThinkPad T60, T60p, T61, T61p 

ThinkPad T410, T410i, T410s, T410si, T510, T510i

ThinkPad T420, T420i, T420s, T420si, T520, T520i
ThinkPad W500, W510, W520

ThinkPad W700, W700ds, W701, W701ds
ThinkPad X1

ThinkPad X61, X61s, X61

TabletThinkPad X121e

ThinkPad X200, X200s, X200, X230

Tablet, X300, X301

ThinkPad X201, X201i, X201s, X201 Tablet

ThinkPad X220, X220i, X220 Tablet

 If maximum frequency operation is preferred in such situations, a 90W AC adapter should be used.

Additionally, operating with battery in circuit offers additional protection of data in the loss of AC input power.

[#2]

However the same issue occurs when you run a W510 with a 90W adapter, even when it's using less than 90W.  Frequently I use my PC on a plane, and my airplane power adapter which delivers 90W makes the PC run at reduced speed and the only way I can get full speed is by running on battery - which is ridiculous.  It would be better to let it run at full speed - OK so if it exceeds 90W of usage then the battery will get drained, but it will still get a longer charge than it would without the power adapter plugged in.

[#3]

Mark,

I just got a T520 with a quad core cpu.  I bought a 65W power supply as after configuring my computer, it was offered as a special for my system and I like to have an extra. When I connect it, I get a message that I have connected the wrong ac adapter and the computer continues to run on battery.  is the 65w power supply adequate to at least charge my computer while it is off?  that is all I really need this extra adapter for anyway.  If it is not, why is it offered with my system?

On another note, the battery life seems pretty good so far.  I have only had my new system for a couple of days but having this much time on battery will be very nice when I travel.

Thanks,

PB

[#4]

To follow up, and, to answer my own question.  The 65w power supply works fine as a battery charger so it will suit my needs nicely when I travel.  The system has plenty of compute power without t-boost and discrete graphics (running optimus mode) that I can get everyting done that I need when I am away and use my system on full power when I am at home or the office.

[#5]

There is no 65 watts adapter for the W70x series.