Theory of Operation 4-3
4.2.2 Memory Subsystem
The memory subsystem comprises the following components:
♦Main memory
♦L2 Secondary Memory (cache)
♦Flash ROM
The Extensa Series uses fast Extended Data Out (EDO) DRAM for main and video
memory and high-speed synchronous, pipelined burst SRAM for L2 cache memory.
Main BIOS and Video BIOS are stored in Flash ROM.

4.2.2.1 Main Memory

The standard 60x Series notebook comes with 8 MB of Main memory installed on the
attached soDIMM. Memory expansion accommodations are provided via a standard
soDIMM connector on the bottom of the Motherboard Assembly.
The 65x Series Notebooks come standard with 16 MB main memory, expandable to
80 MB.

4.2.2.2 Flash ROM

All versions of the Extensa notebook family use a "Flash" ROM that contains both the
main system BIOS and the VGA BIOS. The Flash ROM contains "Boot Block" logic that
allows downloading new versions of BIOS without destroying the Boot Load area.
The Flash ROM execution is 8 bits wide. However, better performance can be attained
by enabling the Shadow ROM in the CMOS setup routine or by selecting the Windows
Control Panel Applet. When the Shadow ROM is enabled, BIOS is copied into 32-bit
high speed system.
4.2.3 V ideo Subsystem
The video subsystem is implemented on the VGA Video Board and on the Motherboard
Assemblies.
The notebook contains a built-in 10.4 inch (or larger) LCD and features simultaneous
LCD and external VGA display.
The video subsystem includes a 1 MB (60x Series) or 2 MB (65x Series) DRAM memory,
32-bit DRAM bus, and separate display and memory clocks. An additional frame buffer/
accelerator DRAM increases the available memory band width for CPU accesses. The