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C h a p t e r 4C h a p t e r 4
Theory of Operation
Service Guide 4-1
4.1. Introduction
This chapter contains a general block diagram theory of operation description of the Extensa 67x
Series Notebook Computers.
Note: Various internal components may change on future models and busses/bus speeds are
subject to change.
4.2. Notebook Functional Overview
The Extensa 67x Series Notebook consist of:
• System Processor - implemented on the Motherboard Assembly
• Memory Subsystem - implemented on the Motherboard Assembly
• Processor/Memory/I/O Control - implemented on the Motherboard Assembly
• Keyboard Subsystem - implemented on the Motherboard and the Keyboard Assemblies
• Video Subsystem - implemented on the Motherboard and on the LCD Display Assembly
• Sound Subsystem - implemented on the Motherboard Assembly.
• Touchpad Mouse Subsystem- implemented on the Touchpad assembly and on the
Motherboard Assembly
• Hard Disk Drive Subsystem - implemented on the Motherboard Assembly and the Hard Disk
Drive Assembly
• Floppy Disk Drive Subsystem - implemented on the Motherboard and Floppy Disk Drive
Assembly
• Power Subsystem - implemented on the Charger Board, Inverter Board, battery packs, and AC
adapter
4.2.1 System Processor
The System Processor function for the notebook is implemented on the Motherboard in the form of
an Intel Pentium P55-C Superscalar 586 Processor Chip. The processor operates in conjunction
with RAM and ROM Memory and other control logic to process software instructions (BIOS, DOS,
Windows, and applications). The processor communicates with the hard disk drive and the memory
components using high speed busses.
The Processor also interacts with other hardware logic to provide the power savings features for the
notebook. These features include controlling CPU clock speeds, reducing clock speeds whenever
possible (e.g. when performing floppy disk drive accesses), powering down unused devices, etc.