Datasheet

20
Chapter 1
Hardware
Power Connectors
A power connector allows the motherboard to be connected to the power supply. On an
ATX, there is a single power connector consisting of a block of 20 holes (in two rows). On
an AT, there is a block consisting of 12 pins sticking up; these pins are covered by two con-
nectors with six holes each.
Figure 1.8 shows a very versatile motherboard that happens to have both kinds, so you
can compare. The upper connector is for ATX, and the lower one is for AT.
FIGURE 1.8 Power connectors on a motherboard
ATX
AT
On-Board Floppy and IDE Connectors
With the exception of diskless workstations, every PC made today uses some type of disk
drive to store data and programs until they’re needed. Disk drives need a connection to
the motherboard in order for the computer to utilize the disk drive. These connections are
known as drive interfaces. There are two primary types: floppy drive interfaces and IDE
interfaces. Floppy drive interfaces allow floppy disk drives to be connected to the moth-
erboard, and, similarly, IDE interfaces do the same for hard disks, CD drives, and other
IDE-based drives. When you see them on the motherboard, these interfaces are said to be
on board, as opposed to being on an expansion card, known as off board. The interfaces
consist of circuitry and a port. A few motherboards also have SCSI interfaces that can be
used for connecting drives.
Battery
Your PC has to keep certain settings when it’s turned off and its power cord is unplugged.
These settings include the date, time, hard drive configuration, and some basic settings
in memory.
86504c01.indd 20 7/25/09 6:04:08 PM