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Models There are hundreds of models of IBM compatible computers. The models of IBM's first-generation Personal Computer (PC) series have names:
The models of its second generation, the Personal System/2 (PS/2), are known by model number: Model 25[?], Model 30[?]. Within each series, the models are also commonly referenced by their CPU clock rate.
All IBM personal computers are software compatible with each other in general, but not every program will work in every machine. Some programs are time sensitive to a particular speed class. Older programs will not take advantage of newer higher-resolution display standards.
The bus used in the original PC became very popular, and was subsequently named ISA. It is in use to this day in computers for industrial use. Later, requirements for higher speed and more capacity forced the development of new versions. The EISA was developed as a backward compatible standard, but due to high complexity and medium performance it dod not really catch on. Instead, the more specialized PCI or AGP busses are now used for expansion cards.
The motherboard is connected by cables to internal storage devices such as hard disks, floppy disks and CD-ROM drives. These tend to be made in standard sizes, such as 3.5" (88.9 mm) and 5.25" (133.4 mm) widths, with standard fixing holes. The case also contains a standard power supply unit (PSU) which is either an AT or ATX standard size.
Intel 8086 and 8088-based PCs require EMS[?] (expanded memory) boards to work with more than one megabyte of memory. The original IBM PC AT used an Intel 80286 processor which can access up to 16 megabytes of memory (though standard MS-DOS applications cannot use more than one megabyte without EMS). Intel 80286-based computers running under OS/2 can work with the maximum memory.
An "IBM PC compatible" may have a keyboard which does not recognize every key combination a true IBM PC does, e.g. shifted cursor keys. In addition, the "compatible" vendors sometimes use proprietary keyboard interfaces, preventing you from replacing the keyboard.
See also: Keyboard layout
In 1984, IBM introduced the 1.2 megabyte dual sided floppy disk along with its AT model. Although often used as backup storage, the high density floppy was not often used for interchangeability. In 1986, IBM introduced the 720 kilobyte 3.5" microfloppy disk on its Convertible laptop computer. It introduced the 1.44 megabyte double density version with the PS/2 line. These disk drives could be added to existing older model PCs.
The first IBM PC that included a fixed, non-removable, hard disks was the XT. Hard disks for IBM compatibles are now available with very large storage capacities. If a hard disk is added that is not compatible with the existing disk controller, a new controller board must be plugged in. However, one disk's internal standard does not conflict with another, since all programs and data must be copied onto it to begin with.
Model name | Introduced | CPU | Features |
---|---|---|---|
PC | Aug 1981 | 8088 | Floppy disk system |
XT | Mar 1983 | 8088 | Slow hard drive |
XT/370 | Oct 1983 | 8088 | IBM 370 mainframe emulation |
3270 PC | Oct 1983 | 8088 | With 3270 terminal emulation |
PCjr | Nov 1983 | 8088 | Floppy-based home computer |
PC Portable | Feb 1984 | 8088 | Floppy-based portable |
AT | Aug 1984 | 286 | Medium-speed hard disk |
Convertible | Apr 1986 | 8088 | Microfloppy laptop portable |
XT 286 | Sep 1986 | 286 | Slow hard disk |
Model | Introduced | CPU | Features |
---|---|---|---|
25 | August 1987 | 8086 | PC bus (limited expansion) |
30 | April 1987 | 8086 | PC bus |
30 | August 1987 | 286 | PC bus |
50 | April 1987 | 286 | Micro Channel Architecture bus |
50Z | June 1988 | 286 | Faster Model 50 |
55 SX | May 1989 | 386SX | MCA bus |
60 | April 1987 | 286 | MCA bus |
70 | June 1988 | 386 | Desktop, MCA bus |
P70 | May 1989 | 386 | Portable, MCA bus |
80 | April 1987 | 386 | Tower, MCA bus |
CPU | Clock speed (MHz) | CPU bus width (bits) | System Bus width (bits) | RAM (megabytes) | Floppy disk drive | Hard drive (megabytes) | Operating System |
---|---|---|---|---|---|---|---|
8088 | 4.77-9.5 | 16 | 8 | 1 (1) | 5.25, 360K 3.5, 720K 3.5, 1.44M | 10-40 | DOS |
8086 | 6-12 | 16 | 20-60 | ||||
286 | 6-25 | 1-8 (1) | 5.25, 360K 5.25, 1.2MB | 20-300 | DOS, OS/2 | ||
386 | 16-33 | 32 | 32 | 1-16 (2) | 3.5, 720K 3.5, 1.44MB | 40-600 | UNIX |
386SX | 16 |
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