IBM Personal Computer XT

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IBM PC/XT (model 5160)

Type	Personal computer
Released	March 8, 1983
Discontinued	1987
Processor	Intel 8088 @ 4.77 MHz
Memory	128KB ~ 640KB
OS	IBM BASIC / PC-DOS 2.0

The IBM Personal Computer XT, often shortened to the PC XT or simply XT, was IBM's successor to the original IBM PC. It was released as IBM product number 5160 on March 8, 1983, and was one of the first computers to come standard with a hard drive. It was based on essentially the same architecture as the original PC, with only incremental improvements; a new 16-bit bus architecture would follow in the AT. The system was largely intended for business users, and a corresponding 3270 PC featuring 3270 terminal emulation was released later in October 1983. XT stands for eXtended Technology.

The XT originally came with 128 kB of memory, a 360 kB double-sided 5 1/4" full-height floppy disk drive, and a 10 MB hard drive, a serial port, eight 8-bit ISA expansion slots, and an Intel 8088 microprocessor running at 4.77 MHz (with a socket for an 8087 math coprocessor); the operating system usually sold with it was PC-DOS 2.0. The eight slots were an increase over the five in the IBM PC, although three were taken up by the floppy drive adapter, the hard drive adapter, and the serial card. Later models came with 256 kB of memory standard, and eventually models with 640 kB and a 20 MB hard drive were sold.

The XT originally came only in a standard configuration with the hard disk. It was not until 1985 that a model without the hard drive became available. Other models came with two half-height floppy drives as well as the hard drive.

In 1986, the XT/286 (IBM 5162) with a 6 MHz Intel 80286 processor was introduced. This system actually turned out to be faster than the ATs of the time using 8 MHz 286 processors due to the fact that it had zero wait state RAM that could move data more quickly.

Like the original PC, the XT came with a BASIC interpreter in ROM. Since this interpreter was meant to be used with a cassette drive (which wasn't offered on the XT), the only ways to access it were by disconnecting the hard drive and leaving the floppy drive empty, using the BASICA program, included on a floppy disk, which added extensions for using the disk drives, or invoking a BIOS call manually using a debugger.

PC and XT keyboards are not compatible with more modern PCs (IBM AT or newer), even with DIN to PS/2 mini-DIN plug adapters, because PC/XT keyboards use different keyboard scan codes. An XT to AT signal adapter is needed to create compatibility with modern computers.