Original PC Hardware Reference

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CD: 18 Original PC Hardware Reference stand, an AC power cord, and a signal cable that connects the 5144 to the CRT display adapter. This display does not resemble—and is not compatible with—the IBM monochrome display for larger PC systems. The CRT adapter emits the same signal as the one supplied by the Color Graphics Adapter for a regular PC. This display is functionally equivalent to the display on the IBM Portable PC. The 5145 PC Convertible color display is a 13-inch color display attached to the system unit through the CRT display adapter. It comes with a display stand, an AC power cord, a signal cable that connects the 5145 to the CRT display adapter, and a speaker for external audio output. The monitor is a low-cost unit compatible with the standard IBM CGA display. Table 5 shows the part numbers of the IBM Convertible system units. Table 5 IBM Convertible Part Numbers 5140 PC Convertible System Units Number Two drives, 256KB with system applications 5140002 Two drives, 256KB without system applications 5140022 An Introduction to the XT (5160) Introduced on March 8, 1983, the PC XT with a built-in 10MB hard disk (originally standard and later optional) caused a revolution in personal computer configurations. At the time, having even a 10MB hard disk was something very special. XT stands for eXTended. IBM chose this name because the IBM PC XT system includes many features not available in the standard PC. The XT has eight slots, allowing increased expansion capabilities, greater power-supply capacity, completely socketed memory, motherboards that support memory expansion to 640KB without using an expansion slot, and optional hard disk drives. To obtain these advantages, the XT uses a different motherboard circuit design than the PC. The system unit was available in several models, with a variety of disk drive configurations: one 360KB floppy disk drive, two 360KB floppy disk drives, one floppy disk and one hard disk drive, or two floppy disk drives and one hard disk drive. The floppy disk drives were full-height drives in the earlier models and half-height drives in more recent models. With the four available drive bays, IBM had standard configurations with two floppy drives and a single hard disk, with room for a second hard disk provided all half-height units were used. IBM offered only 10MB and 20MB full-height hard disks. In some cases, they also installed halfheight hard disks, but they were always installed in a bracket-and-cradle assembly that took up the equivalent space of a full-height drive. If you wanted half-height hard disks (to install two of them stacked, for example), you had to use non–IBM-supplied drives or modify the mounting of the IBM-supplied half-height unit so that two could fit. Most aftermarket sources for hard disks had mounting kits that would work. IBM also used double-sided (320/360KB) floppy disk drives in full- or half-height configurations. A 3 1/2-inch, 720KB floppy disk drive was available in more recent models. The 3 1/2-inch drives
An Introduction to the XT (5160) CD: 19 were available in a normal internal configuration or as an external device. You could install a maximum of two floppy disk drives and one hard disk drive in the system unit, using IBM-supplied drives. With half-height hard disks, you could install two hard drives in the system unit. The XT is based on the same 8- and 16-bit Intel 8088 microprocessor (the CPU has 16-bit registers but only an 8-bit data bus) as the PC and runs at the same clock speed. Operationally, the XT systems are identical to the PC systems except for the hard disk. All models have at least one 360K floppy disk drive and a keyboard. For standard memory, the XT offers 256K or 640K on the main board. The hard disk models also include a serial adapter. The system unit has eight slots that support cards for additional devices, features, or memory. Two of the slots support only short option cards because of physical interference from the disk drives. The XT has at least a disk drive adapter card in the floppy-disk–only models, and a hard disk controller card and serial adapter in the hard disk models. Either five or seven expansion slots (depending on the model) are available. Figure 5 shows the interior of an XT. Option adapters Figure 5 The IBM PC XT interior. System board Power supply Speaker Floppy disk drive A Hard disk drive C
Page 1 and 2: This is the Current C-Head at the B
Page 3 and 4: An Introduction to the PC (5150) CD
Page 5 and 6: Option adapters Figure 1 The IBM PC
Page 7 and 8: An Introduction to the PC (5150) CD
Page 9 and 10: Read-only memory { 64K to 256K read
Page 11 and 12: Expansion Slots Total adapter slots
Page 13 and 14: An Introduction to the PC Convertib
Page 15 and 16: ■ Serial/parallel adapter (#4015)
Page 17: An Introduction to the PC Convertib
Page 21 and 22: An Introduction to the XT (5160) CD
Page 23 and 24: An Introduction to the XT (5160) CD
Page 25 and 26: Disk Storage An Introduction to the
Page 27 and 28: Switch Block 1 (PC and XT) Switch 5
Page 29 and 30: An Introduction to the Portable PC
Page 31 and 32: Disk Storage Internal disk and tape
Page 33 and 34: IBM also offered only three differe
Page 35 and 36: Power switch Power supply selector
Page 37 and 38: An Introduction to the AT CD: 37 Th
Page 39 and 40: An Introduction to the AT CD: 39 AT
Page 41 and 42: An Introduction to the AT CD: 41 Ty
Page 43 and 44: Table 10—Drive Types An Introduct
Page 45 and 46: Memory An Introduction to the AT CD
Page 47 and 48: Variable capacitor clock trimmer RO
Page 49 and 50: An Introduction to the XT Model 286
Page 51 and 52: ■ 1.2MB floppy drive ■ 20MB har
Page 53 and 54: Disk Storage An Introduction to the
Page 55: CMOS RAM/RTC 8259 Interrupt control

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