Original PC Hardware Reference

■ 1.2MB floppy drive
■ 20MB hard disk
■ Five 16-bit and three 8-bit expansion slots
An Introduction to the XT Model 286 CD: 51
■ Fixed disk/floppy disk drive adapter (occupies one 16-bit expansion slot)
■ Serial/parallel adapter (occupies one 16-bit expansion slot)
■ Enhanced 101-key keyboard with indicator lights
■ CMOS time and date clock with battery backup
XT Model 286 Models and Features
The XT Model 286 processor is as much as three times faster internally than the preceding XT
family and as much as 25 percent faster than the AT Model 239, depending on specific applications.
A 20MB fixed disk and a 1.2MB 5 1/4-inch floppy disk drive were standard on the XT
Model 286. One additional floppy disk drive can be installed internally as drive B. You can add as
a second half-height floppy drive any type of floppy drive, including both the double- and highdensity
versions of the 5 1/4- and 3 1/2-inch drives.
If you want to be able to read standard 5 1/4-inch data or program floppy disks created by the XT
Model 286 on other PC systems, you might want to add a 5 1/4-inch 360KB floppy disk drive to
provide full read/write compatibility with those systems. This is due to the fact that the 1.2M drives
write a narrower track than the 360KB drives and are incapable of properly overwriting a
floppy disk written on first by a 360KB drive. If full read/write compatibility with 360KB drives is
not important, you can add a second 1.2MB high-density floppy disk drive.
You can add any 3 1/2-inch drive, including the 720KB and 1.44MB versions. Because the 1.44MB
does not have any read/write compatibility problems with the 720KB drives, however, and the
1.44MB drives always can operate in 720KB mode, I suggest adding only the 1.44MB 3 1/2-inch
drives rather than the 720KB versions. The higher density drive is only a small extra expense
compared to the double-density version. Most people do not know that full ROM BIOS support
for these 1.44MB drives is provided in the XT Model 286. Unfortunately, because IBM never
offered the 1.44MB drive as an option, the supplied Setup program does not offer the 1.44MB
drive as a choice in the Setup routine. Instead, you have to use one of the many available public
domain AT type setup programs, or “borrow” such a program from an AT-compatible system.
XT Model 286 Technical Specifications
The technical information for the XT-286 system described in this section covers the system
architecture, memory configurations and capacities, standard system features, disk storage, expansion
slots, keyboard specifications, and also physical and environmental specifications. You can
use this information to determine the parts you need when you are upgrading or repairing these
systems. Figure 14 shows the layout and components on the XT-286 motherboard.