IBM Thinkpad T40 Hardware Maintenance Manual page 145

Removing and replacing a FRU
Important notice for handling the system board in
ThinkPad T41 series:
In ThinkPad T41 series, the security chip a is soldered
on the underside of the system board as in this figure.
a
In ThinkPad T41 series, accelerometer chip for the HDD
Active Protection System b is also soldered on the
topside of the system board.
b
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ThinkPad T40/T40p, T41/T41p, T42/T42p Series