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Born in August 1981 due to the [[Apple II]]'s success, the IBM Personal Computer (dubbed the "5150" in IBM's internal numbering system) was IBM's official entry into the desktop computer system market, and by far their most successful. Earlier attempts, like the 5100 desktop APL machine and the DisplayWriter word-processing machine, hadn't taken off, and IBM needed something ''fast'' to compete with Apple. Bypassing the IBM bureaucracy, in 1980 they tasked a team of engineers in an IBM office in Florida with developing the new machine, and gave them unusual amounts of freedom in developing the new system. It was built almost completely out of off-the-shelf parts and had generous amounts of expansion capability. As for the processor, the team settled on Intel's 16-bit 8088. The 8088 was chosen mainly for cost and time-to-market reasons. To ensure a steady supply of 8088s, IBM and Intel recruited Advanced Micro Devices (AMD) to act as a second source, a decision that would have some importance later.
 
== History ==
 
It was nothing like any IBM machine built before. Like the Apple II, it was built almost completely out of off-the-shelf parts and had generous amounts of expansion capability. As for the processor, the team settled on Intel's 16-bit 8088. The 8088 was chosen mainly for cost and time-to-market reasons; the ROMP was still experimental and IBM was concerned that the 68000 wouldn't be available in quantity. Also, the 8088 could re-use many of the support chips Intel had designed for the 8085, making the motherboard design simpler. To ensure a steady supply of 8088s, IBM and Intel recruited Advanced Micro Devices (AMD) to act as a second source, a decision that would have some importance later.
 
The other big influence on the IBM PC's design was the world of ''S-100 machines'', which were based around the Intel 8080 (or, later the Zilog Z80) and the "S-100" bus that had been introduced in the pioneering Altair 8800. These machines ran an OS called ''CP/M'', which had been invented by a programmer named Gary Kildall in 1974 and was based indirectly on Digital Equipment Corp.'s ''RSX-11'' [[Operating System]] for the PDP-11. While they weren't nearly as slick as the [[Apple II]], S-100 machines were popular with hobbyists and businesses alike, and several CP/M applications for businesses, like ''WordStar'' and ''dBASE'' were making inroads.
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=== IBM Tries to Win Back the Crowd ===
With all of the pieces in place, the clone market took off like a shot after 1984. New companies building PCs based on cheap, mass-market "motherboards" made in factories in East Asia were popping up everywhere, and Compaq became a Fortune 500 company on the success of its Portable and Deskpro ranges. In 1986 Compaq beat IBM to the punch with the first PC to use the new, 32-bit 80386 processor. Between the clone armies and Compaq's meteoric rise, IBM decided that if it couldn't compete on price, it would compete on features, and (it was hoped) introduce a new standard that they alone would control.
 
The result was the ''Personal System/2'' (or PS/2 for short), a line of new PC-based machines that were deliberately much different from the prevailing PC standards. The new machines used a new, IBM-proprietary expansion bus called "Micro Channel", which was faster than the AT's bus (by now referred to as "ISA" for "Industry Standard Architecture") but completely incompatible ''and'' protected by IBM patents, requiring anyone who wanted to use it to go through a lengthy licensing process and pay royalties. The other major feature the PS/2 line introduced was a new video subsystem called Video Graphics Array (VGA), a substantial upgrade to EGA that added a new 640×480 high-resolution mode (familiar now as the mode Windows 2000 and XP use for their splash screens), analog RGB video with an 18-bit palette (over 262,000 colors), and up to 256 colors on-screen at once. VGA was accepted by the rest of the industry enthusiastically, with 100% VGA compatibility becoming a must for video-card makers.
 
The VGA proved very popular with game developers. What it lacked in tricks like sprites, blitting and scanline DMA, it compensated for by being tweakable (hacked 256-color modes were very popular, providing resolutions up to 360×480) and having high-speed, easy-to-use video memory. The base 320×200x256 mode, however, was the easiest and the fastest<ref>Mainly because, at 64 000 bytes, it fit neatly into the one 64K segment, by which x86 CPUs addressed their memory in "real mode" (the main one back in the DOS era), thus freeing the programmer from fussing around with the segment registers.</ref>, and many groundbreaking games of the late 1980s and early 1990s were written with this mode in mind, including the Sierra and Lucasfilm point-and-click adventures, ''[[Wolfenstein 3D]]'' and ''[[Doom (series)|Doom]]''. 640x480x16 mode, on the other hand, was extremely popular with the early graphical OSes and GUI-based DOS software, and it remains a barebone compatibility video mode in many ''modern'' OSes as well. Later IBM innovations, like 1024x768x16 XGA, were a few more-or-less standard modes in the swirling chaos generally known as "Super VGA".
 
 
=== Wintel Comes And Wins ===
After years of being confined to what were basically fleet sales, IBM discontinued the PS/2 line and MCA in the mid-1990s, preferring instead to concentrate on the revived "IBM PC" brand (new, ISA/PCI-based machines sold as business desktops) and the highly successful ThinkPad line of notebooks, which was introduced in 1992. This marked the end of IBM's dominance of the PC clone market, with the balance of power now shifted to Microsoft, Intel and the clonemakers.
 
Today, in early 2011, the PC's various implementations are collectively the most popular desktop computer in the world, and have even made inroads into scientific and high-performance computing due to huge leaps in processing capability as well as an emphasis on power savings. Several attempts to update the PC using newer parts have come and gone; most of them failed after 1995 as the PC's hardware ended up absorbing most of the features that a switch to MIPS or PowerPC would have brought, including (eventually) the RISC philosophy itself. The Pentium Pro and its descendants are actually RISC processors internally, and use emulation to handle the rather haphazard x86 ISA instead of trying to execute it directly, as all processors up to the Pentium had.
 
On top of all this, the rise of the clones meant that pretty much everyone was selling nearly identical systems with little to differentiate them; this made margins even tighter and made PC makers more reliant on advertising, system aesthetics (the aforementioned ThinkPad was one of the first PCs to buck the trend of the generic beige box), gimmicks such as "100x CD-ROM" software and other pack-ins, and, if all else failed, price. This environment made it much more difficult for a new player to enter, as any new system would almost certainly be more expensive than a regular PC would and would have the additional hassles of porting all the software. Apple was able to stick it out due to both clever advertising and innovative system design, but they, too, eventually switched to x86 in 2006.
 
 
As a footnote, IBM themselves left the personal computer business for good in 2005, selling their PC division to a Chinese company named Lenovo (hence Lenovo now sells the Thinkpad).
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