Datasheet

38 Chapter 1
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Hardware
HDD Auto Detection
Some CMOS Setup programs have a feature that polls the IDE channels and provides infor-
mation about the IDE devices attached to them. You can use this feature to gather the set-
tings for a hard disk. However, most hard disks these days are fully Plug and Play, so they
automatically report themselves to the CMOS Setup.
Drive Configuration
You can specify how many floppy drives are installed and what types they are. Floppy drives
aren’t automatically detected. The settings needed for a floppy drive are size (3
1
⁄2-inch or
5¼-inch) and density (double-density or high-density). You can also set each floppy drive to
be enabled or disabled from being bootable. Almost all floppy drives today are high-density
3
1
⁄2-inch.
Hard drives, on the other hand, can be autodetected by most systems if the IDE setting is
set to Auto. The settings detected may include the drive’s capacity; its geometry (cylinders,
heads, and sectors); and its preferred PIO (Programmed Input/Output), direct memory access
(DMA), or UltraDMA operating mode. You can also configure a hard drive by entering its
CHS values manually, but doing so is almost never necessary anymore.
CHS stands for cylinders, heads, and sectors. This is also called the drive
geometry, because together these three numbers determine how much
data the disk can hold. Most CMOS Setup programs are able to automati-
cally detect the CHS values.
Boot Sequence
Each system has a default boot order, which is the order in which it checks the drives for a
valid operating system to boot. Usually, this order is set for floppy first, then hard disk, and
finally CD-ROM, but these components can be placed in any boot order. For example, you
might set CD-ROM first to boot from a Windows XP Setup disk on a system that already
contained an operating system.
Exiting CMOS Setup
The CMOS Setup program includes an Exit command, with options that include Save
Changes and Discard Changes. In most programs, Esc is a shortcut for exiting and dis-
carding changes, and F10 is a common shortcut for exiting and saving changes.
BIOS Issues
Computer BIOSs don’t go bad; they just become out-of-date. This isn’t necessarily a critical
issue—they will continue to support the hardware that came with the box. It does, however,
become an issue when the BIOS doesn’t support some component that you would like to
install—a larger hard drive, for instance.
Most of today’s BIOSs are written to an EEPROM and can be updated through the use
of software. Each manufacturer has its own method for accomplishing this. Check out the
documentation for complete details.
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