IBM 560E manual Memory, ROM Subsystem, RAM Subsystem

Memory

The ThinkPad computers use the following types of memory:

Ÿ Read-only memory (ROM)

Ÿ Random access memory (RAM)

ŸReal-time clock/complementary metal-oxide semiconductor RAM (RT/CMOS RAM)

ROM Subsystem

The	ROM	subsystem consists				of	four banks of 128KB memory.
ROM	is	active		when	power	is	turned on		and is assigned to the top of
the	first		and	last	1MB of address space (hex 000F0000–000FFFFF
and	hex FFFF0000–FFFFFFFF).				After POST checks that system
memory		is	operating		correctly,		the	ROM	code is copied to RAM at
the	same		address		space,	and	ROM	is	disabled.

RAM Subsystem

The	RAM	subsystem on the	system	board starts		at address
hex 00000000 of the address space. The RAM					subsystem		for the
ThinkPad		560 is 64 bits wide.
The	8MB	(ThinkPad 560) or 16MB (ThinkPad 560E)			base	memory	is
on	the	system board. One	144-pin	8-byte	dual	inline	memory

module (DIMM) connector is provided on the system board. This

connector accepts a			8MB,	16MB,	32MB, 1 orDIMM64MB.The
memory	capacity	can	be	increased up		to 40MB (ThinkPad 560) or
80MB (ThinkPad 560E)		when a		DIMM	is used	(see “System Board
Memory	Connector	for	DIMM” on		page 2-14).

The total amount of usable memory is less than the amount of memory installed because of ROM-to-RAM remapping and power management.

1 A 64MB DIMM is supported by ThinkPad 560E only.

ThinkPad 560/560E System Board 2-13