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The IBM Personal Computer XT, often shortened to the IBM XT, PC XT, or simply XT, is a version of the IBM PC with a built-in hard drive. It was released as IBM Machine Type number 5160 on March 8, 1983. Apart from the hard drive, it was essentially the same as the original PC, with only minor improvements. The XT was mainly intended as an enhanced IBM PC for business users. Later floppy-only models would effectively replace the original model 5150 PC. A corresponding 3270 PC featuring 3270 terminal emulation was released later in October 1983. XT stands for eXtended Technology. == Features == The IBM Personal Computer XT originally came with 128 KB of RAM, a 360 KB double-sided 5¼ inch floppy disk drive, a 10 MB Seagate ST-412 hard drive with Xebec 1210 Modified Frequency Modulation (MFM) controller, an Asynchronous Adapter (serial card with 8250 UART), and a 130-watt power supply.〔Scott Mueller, "Upgrading and Repairing PCs 2nd Edition" Que Books, 1992 ISBN 0-88022-856-3, pp. 59-79〕 The motherboard had an Intel 8088 microprocessor running at 4.77 MHz, with a socket for an optional 8087 math coprocessor. IBM recognized soon after the IBM PC's release in 1981 that its five 8-bit "I/O channel" expansion slots (later named Industry Standard Architecture (ISA) by IBM's competitors) were insufficient. An internal IBM publication stated in October 1981 about the number that "In my opinion, it could be a problem", reporting that others within IBM advised swapping cards if necessary. Virtually every PC required at least a display adapter card and a floppy disk controller card, leaving only three slots available for a parallel printer port card (if the Color Graphics Adapter was used), a serial port card, memory expansion boards, a 3rd-party hard disk controller card, a second display adapter card, or possible other special adapter cards. The XT had eight slots, although the floppy and hard drive adapters, the serial port card, and nearly always a display adapter board occupied slots. The basic specification was soon upgraded to have 256 KB of RAM as standard. Expansion slots could be used for I/O devices or for memory expansion. Video cards initially comprised the Monochrome Display Adapter (MDA) and Color Graphics Adapter (CGA) (the same two cards that were available for the type 5150 PC), with Enhanced Graphics Adapter (EGA) and Professional Graphics Controller (PGC) becoming available in 1984. The XT had a desktop case similar to that of the IBM PC. It weighed 32 pounds and was approximately 19.5 inches wide by 16 inches deep by 5.5 inches high. The power supply of the original XT sold in the US was configured for 120 V AC only and could not be used with 240 V mains supplies.〔 XTs with 240V-compatible power supplies were later sold in international markets. Both were rated at 130 Watts.〔 The operating system usually sold with the XT was PC DOS 2.0 or, by the time the XT was discontinued in early 1987, DOS 3.2. Like the original PC, the XT came with IBM BASIC in its ROM. Despite the lack of a cassette port on XTs, IBM's licensing agreement with Microsoft forced them to include BASIC on all their PCs, and the BASICA program that was included with DOS depended on the BASIC ROM. The XT BIOS also displayed a memory count during the POST, unlike the PC. The XT was discontinued in the spring of 1987, replaced by the PS/2 Model 30. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「IBM Personal Computer XT」の詳細全文を読む スポンサード リンク
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