IBM manual Viii ThinkPad 560/560E Preface

	Attention
The termReserved describes certain		signals, bits,	and	registers
that should not be changed. Use of reserved			areas can cause
compatibility problems, loss of data, or permanent			damage to the
hardware. When the contents of a		register are	changed,		the
state of the reserved bits must		be preserved.	When possible,
read the register first and change only the			bits	that	must be
changed.

viii ThinkPad 560/560E Preface