4-6 Theory of Operation
external microphone and line inputs and headphone/speaker outputs.
The sound subsystem also includes a variety of sound utilities that combine to
provide additional multi-media functions:
4.2.6 Keyboard Subsystem
The keyboard subsystem, implemented on the Keyboard Assembly and the System
Board Assemblies Board, consists of the following major sections:
♦Keyboard Assembly
♦Keyboard Scanner
♦Status LED Interface
4.2.7 Hard Disk Drive Subsystem
The Hard Disk Drive Subsystem, implemented on the System Board and on the
associated hard disk drive module(s), provides disk storage for all system software
and user files.
The notebook is equipped with a high-capacity hard disk drive. The hard disk drive also
features built-in power conservation features configured from the standard CMOS
Setup Routine. An Automatic Power Down mode can be selected which powers down
the drive motor during periods of inactivity. An additional level of power conservation
may also be selected which powers down the motor plus all control circuits.
The hard disk drives are factory formatted as a single drive (Drive C:) and are preloaded
with installation versions of Windows 95 or Windows for Workgroups (in dual load
versions, the user selects the operating system during software installation).

4.2.7.1 Hard Disk Drive Power Management

Both the internal hard disk drive and the hard disk drive installed in the media bay
implement power savings features. From the CMOS setup routine, an automatic
power down mode can be selected which enables the drive to turn off its motor after a
specified period of inactivity. Additional Sleep modes can direct additional power
savings during inactive periods by powering down the control circuitry.
4.2.8 Floppy Disk Drive Subsystem
The Extensa 660 is equipped with a 3.5-inch floppy disk drive in the media bay that
can read/write standard 3.5-inch disks (either1.44 MB or 2 MB capacity). The drive
can also read a 720 KB disk (for interchange of data with other computers).
The data transfer rate for the floppy disk drive is 500 Kbits per second for high-
density disks and 250 Kbits per second for double-density disks.