IBM X23 - Manual (Page 51)

Memory
1. If two DIMMs are installed, remove one
of them and run Diagnostics -->
Memory Test - Quick.
2. If the problem does not recur, replace
the DIMM, remove the other one, and
run the test again.
3. If the test does not detect the error, run
Diagnostics --> Memory Test - Full.
Fan
1. Turn on the computer and check the air
turbulence at the louver near the power
switch.
2. Run Diagnostics --> Other Devices -->
IBM Fan.
Fn key combinations
The following table shows the function of each combination
of Fn with a function key.
The Fn key works independently from the operating
system.
Key Combination Result
Fn + F1 Reserved.
Fn + F2 Reserved.
Fn + F3 Standby mode.
Fn + F4 Suspend mode.
Fn + F5 Reserved.
Fn + F6 Reserved.
Fn + F7 Switch between the LCD, the external
monitor, and both the LCD and external
monitor.
Fn + F8 Reserved.
Fn + F9 Reserved.
Fn + F12 Hibernation mode.
Fn + PgUp ThinkLight On/Off.
Fn + Home The LCD becomes brighter.
Fn + End The LCD becomes less bright.
Chapter 3. ThinkPad X20, X21, X22, X23, X24 47