IBM Personal Computer XT

IBM did not specify an expanded form of "XT" on the machine, press releases, brochures or documentation, but some publications expanded the term as "eXtended Technology" or just "eXTended". == Features ==

The XT was regarded as an incremental improvement over the PC and a disappointment compared to the next-generation successor that some had anticipated. Compared to the original IBM PC, the XT has the following major differences: • The number of expansion slots was increased from five to eight • Base RAM was increased to at least 128 KB • 5x8 KB ROM ICs was replaced by 2x32 KB one • A 10 MB hard drive was included on most sub-models, with a disk controller featuring Xebec ICs • PC DOS 2.0 was included • The 5-pin DIN for the cassette interface was removed Otherwise the specifications are identical to the original PC. Expansion slots The number of expansion slots in the original IBM PC was a limiting factor for the product, since essential components (such as the video controller, disk controller and printer interface) each came as separate expansion cards and could quickly fill up all five available slots, requiring the user to swap cards in and out as tasks demanded. Some PC clones addressed this problem by integrating components into the motherboard to free up slots, while peripheral manufacturers produced products which integrated multiple functions into one card. The XT addressed the problem by adding three extra expansion slots for a total of eight. While the slots themselves are identical to those in the original PC, the amount of physical space in the chassis differs, so two of the new slots (located behind the hard drive) cannot accept full-length cards. In addition, the spacing of the slots is narrower than in the original PC, making it impossible to install some multi-board cards. Other features PC DOS 2.0 offers a 9-sector floppy disk format, providing 180K/360K (single- vs. dual-sided) capacity per disk, compared to the 160K/320K provided by the 8-sector format of previous releases. XTs with 240 V-compatible power supplies were later sold in international markets. Both were rated at 130 watts. ==Revisions and variants==

IBM made several submodels of the XT. The 3270 PC, a variant of the XT featuring 3270 terminal emulation, was released in October 1983. Submodel 068 and 078, released in 1985, offered dual-floppy configurations without a hard drive as well, and the new Enhanced Graphics Adapter and Professional Graphics Adapter became available as video card options. In 1986, the 256–640 KB motherboard models were launched, which switched to half-height drives. Submodels 268, 278 and 089 came with 101-key keyboards (essentially the IBM Model M, but in a modified variant that used the XT's keyboard protocol and lacked LEDs). Submodels 267, 277 and 088 had the original keyboard, but 3.5" floppy drives became available and 20MB Seagate ST-225 hard disks in 5.25" half-height size replaced the full-height 10 MB drives. Submodel 788 was the only XT sold with the Color Graphics Adapter as a standard feature. An XT-based machine with a Series/1 co-processor board existed as well, but it had its own System Unit number, the IBM 4950. XT 286 In 1986, the XT 286 (model 5162) was released with a 6 MHz Intel 80286 processor. Despite being marketed as a lower-tier model than the IBM AT, this system runs many applications faster than the ATs of the time with 6 MHz 286 processors, since it has zero-wait state RAM. Despite these features, reviews rated it as a poor market value. The XT 286 uses a 157-watt power supply, which can internally switch between 115 or 230 V AC operation. Both the original XT and the XT/286 was discontinued in late 1987 after the launch of the IBM Personal System/2 (PS/2) line. The 8086-powered IBM PS/2 Model 30 served as the direct replacement for the XT in that PS/2 line. Unlike higher-end entries in the PS/2 line, which feature the Micro Channel expansion bus, the Model 30 contains 8-bit ISA bus slots, exactly like the XT. Comparison table ==Reception==

The XT was well received, although PC DOS 2.0 was regarded as a greater improvement than any of the hardware changes, and by the end of 1983 IBM was selling every unit they made. By 1985 the IBM PC AT made the XT obsolete for most customers. ==Timeline==