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86-587: The IBM Personal Computer AT (model 5170, abbreviated as IBM AT or PC/AT ) was released in 1984 as the fourth model in the IBM Personal Computer line, following the IBM PC/XT and its IBM Portable PC variant. It was designed around the Intel 80286 microprocessor . IBM did not specify an expanded form of AT on the machine, press releases, brochures or documentation, but some sources expand

172-495: A HD read head would only pick up the half track that drive had written, the wider DD read head would pick up the half-track written by the HD drive mixed with the unerased half-track remnant of the track written earlier by a DD drive. Thus, the DD drive would end up reading both new and old information together, causing it to see garbled data. Due to a US antitrust consent decree with IBM,

258-670: A battery-backed real-time clock (RTC) using the Motorola MC146818. This was an improvement from the PC, which required setting the clock manually or installing an RTC expansion card. The RTC also included a 1024 Hz timer (on IRQ 8), a much finer resolution than the 18 Hz timer on the PC. In addition to keeping the time, the RTC includes 50 bytes of CMOS memory which is used to store software-adjustable BIOS parameters. A disk-based BIOS setup program which saved to this memory took

344-549: A comparable computer at COMDEX Las Vegas that year. The AT is IBM PC compatible , with the most significant difference being a move to the 80286 processor from the 8088 processor of prior models. Like the IBM PC, the AT supported an optional math co-processor chip, the Intel 80287 , for faster execution of floating point operations . In addition, it introduced the AT bus , later known as

430-420: A computer through retail channels rather than directly to customers. Because IBM did not have retail experience, they partnered with the retail chains ComputerLand and Sears , who provided important knowledge of the marketplace and became the main outlets for the PC. More than 190 ComputerLand stores already existed, while Sears was in the process of creating a handful of in-store computer centers for sale of

516-442: A dedicated power supply and included a hard drive. Although official hard drive support did not exist, the third party market did provide early hard drives that connected to the floppy disk controller , but required a patched version of PC DOS to support the larger disk sizes. The only option for human interface provided in the base PC was the built-in keyboard port, meant to connect to the included Model F keyboard. The Model F

602-445: A design could be delivered within a year and a prototype within 30 days. The prototype worked poorly but was presented with a detailed business plan which proposed that the new computer have an open architecture , use non-proprietary components and software, and be sold through retail stores, all contrary to IBM practice. It also estimated sales of 220,000 computers over three years, more than IBM's entire installed base . This swayed

688-507: A few on the older pattern continued to be made at Greenock and Guadalajara until 1999. Relatively few press-fit model Ms have survived. During the Lexmark years, a few Model M variants were manufactured with rubber-dome key switches rather than buckling springs. Due to these switches' comparatively short durability, few of these variants have survived. Despite their rarity, today's enthusiasts and collectors do not value them nearly as highly as

774-463: A grounded spacebar and, on some later models, drainage holes to deter damage from spilled liquids. The M2 was a late Lexmark variation issued under cost pressure from competing rubber-dome keyboards. Some revisions used rubber-dome switches; others retained buckling springs. All had a much thinner, lighter case and discarded the metal backplate. It can easily be distinguished from the original Model M design by its flat, unsculpted front case section; also

860-525: A hard drive were shipped with a 5-ohm, 50-watt resistor connected on the +12 V line of the hard disk power connector. In normal operation this resistor drew 2.4 amperes (dissipating 28.8 watts), getting fairly hot. In addition to the unreliable hard disk drive, the high-density floppy disk drives turned out to be problematic. Some ATs came with one high-density (HD) disk drive and one double-density (DD) 360 KB drive. High-density floppy diskette media were compatible only with high-density drives. There

946-583: A hard drive, the motherboard did not support BIOS expansion ROMs which was needed to support a hard drive controller, and both PC DOS and the BIOS had no support for hard disks. After the XT was released, IBM altered the design of the 5150 to add most of these capabilities, except for the upgraded power supply. At this point adding a hard drive was possible, but required the purchase of the IBM 5161 Expansion Unit, which contained

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1032-567: A library of common functions that all software can use for many purposes, such as video output, keyboard input, disk access, interrupt handling, testing memory, and other functions. IBM shipped three versions of the BIOS throughout the PC's lifespan. While most home computers had built-in video output hardware, IBM took the unusual approach of offering two different graphics options, the MDA and CGA cards. The former provided high-resolution monochrome text, but could not display anything except text, while

1118-401: A maximum of 64 KB onboard, and the more common 64 KB revision to a maximum of 256 KB on the motherboard. RAM cards could upgrade either variant further, for a total of 640 KB conventional memory , and possibly several megabytes of expanded memory beyond that, though on PC/XT-class machines, the latter was a very expensive third-party hardware option only available later in

1204-657: A mouse.) Connectivity to other computers and peripherals was initially provided through serial and parallel ports. IBM provided a serial card based on an 8250 UART . The BIOS supports up to two serial ports. IBM provided two different options for connecting Centronics-compatible parallel printers. One was the IBM Printer Adapter, and the other was integrated into the MDA as the IBM Monochrome Display and Printer Adapter. The expansion capability of

1290-609: A number of different interface and connector standards, some of which (such as the 5-pin DIN used on 5250 terminals) are poorly documented and have had to be reverse-engineered by enthusiasts. Early variants shipped with the PC XT and AT used connectors specific to those systems. After the introduction of the PS/2 most shipped with a connector for a PS/2 port ; these included the 1391401. Unicomp introduced support for USB . Older model Ms used

1376-505: A policy of strict secrecy, with all other IBM divisions kept in the dark about the project. Several CPUs were considered, including the Texas Instruments TMS9900 , Motorola 68000 and Intel 8088 . The 68000 was considered the best choice, but was not production-ready like the others. The IBM 801 RISC processor was also considered, since it was considerably more powerful than the other options, but rejected due to

1462-595: A separate monochrome monitor for text menus. Third parties went on to provide an enormous variety of aftermarket graphics adapters, such as the Hercules Graphics Card . The software and hardware of the PC, at release, was designed around a single 8-bit adaptation of the ASCII character set, now known as code page 437 . The two bays in the front of the machine could be populated with one or two 5.25″ floppy disk drives, storing 160 KB per disk side for

1548-459: A total of 320 KB of storage on one disk. The floppy drives require a controller card inserted in an expansion slot, and connect with a single ribbon cable with two edge connectors. The IBM floppy controller card provides an external 37-pin D-sub connector for attachment of an external disk drive, although IBM did not offer one for purchase until 1986. As was common for home computers of the era,

1634-424: A well publicized quote from an industry analyst was, "IBM bringing out a personal computer would be like teaching an elephant to tap dance." IBM had previously produced microcomputers, such as 1975's IBM 5100 , but targeted them towards businesses; the 5100 had a price tag as high as $ 20,000. Their entry into the home computer market needed to be competitively priced. In 1980, IBM president John Opel, recognizing

1720-403: A year. By 1984, IBM's revenue from the PC market was $ 4 billion, more than twice that of Apple. A 1983 study of corporate customers found that two thirds of large customers standardizing on one computer chose the PC, while only 9% chose Apple. A 1985 Fortune survey found that 56% of American companies with personal computers used PCs while 16% used Apple. Almost as soon as the PC reached

1806-411: Is housed in a wide, short steel chassis intended to support the weight of a CRT monitor. The front panel is made of plastic, with an opening where one or two disk drives can be installed. The back panel houses a power inlet and switch, a keyboard connector, a cassette connector and a series of tall vertical slots with blank metal panels which can be removed in order to install expansion cards. Internally,

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1892-901: The 5250 terminal and the RS/6000 . They were produced at IBM plants in Lexington, Kentucky ; Greenock, Scotland ; and Guadalajara, Mexico . The most common variant is the IBM Enhanced Keyboard identified by IBM assembly part number 1391401, the U.S. English layout keyboard bundled with the IBM Personal System/2 . Until around 1993, most Model Ms included a coiled, detachable cable, with either an AT (pre-1987) or PS/2 connector , in 5- and 10-foot lengths (1.5 and 3 meters). From about 1994 onwards, flat non-detachable cables were used to reduce manufacturing costs; however, IBM retained its 101-key layout, never implementing

1978-640: The IBM System/23 Datamaster . The 62-pin expansion bus slots were also designed to be similar to the Datamaster slots, and its keyboard design and layout became the Model F keyboard shipped with the PC, but otherwise the PC design differed in many ways. The 8088 motherboard was designed in 40 days, with a working prototype created in four months, demonstrated in January 1981. The design

2064-607: The IBM System/370 , and Matsushita acknowledged publicly that it had discussed with IBM the possibility of manufacturing a personal computer in partnership, although this project was abandoned. The public responded to these rumors with skepticism, owing to IBM's tendency towards slow-moving, bureaucratic business practices tailored towards the production of large, sophisticated and expensive business systems. As with other large computer companies, its new products typically required about four to five years for development, and

2150-737: The Microsoft Windows keys common on other keyboards from that time. Unicomp later designed a 104-key Model M with Windows keys. On March 27, 1991, IBM divested a number of its hardware manufacturing operations, including keyboard production, forming Lexmark International . Lexmark continued manufacturing Model M keyboards in the United States, United Kingdom, and Mexico, with IBM as their major customer. Many of these keyboards are identified by IBM assembly part numbers 52G9658, 52G9700, 71G4644, 82G2383, and 42H1292, which were bundled with IBM PS/ValuePoint and IBM PC Series . Over

2236-455: The 130-watt XT power supply. According to IBM's documentation, in order to function properly, the AT power supply needed a load of at least 7.0 amperes on the +5 V line and a minimum of 2.5 amperes on its +12 V line. The power supply would fail to start unless these minimum load requirements were met, but the AT motherboard did not provide much load on the +12 V line. To solve this problem, entry-level IBM AT models that did not have

2322-407: The 1980s opened, their market share in the growing minicomputer market failed to keep up with competitors, while other manufacturers were beginning to see impressive profits in the microcomputer space. The market for personal computers was dominated at the time by Tandy , Commodore , and Apple , whose machines sold for several hundred dollars each and had become very popular. The microcomputer market

2408-415: The 1980s was from Apple 's Macintosh product line, as well as consumer-grade platforms created by companies like Commodore and Atari . Most present-day personal computers share architectural features in common with the original IBM PC, including the Intel -based Mac computers manufactured from 2006 to 2022 . Prior to the 1980s, IBM had largely been known as a provider of business computer systems. As

2494-504: The 1990s amid an industry-wide switchover to lower-cost rubber dome over membrane keyboards. IBM stopped producing the Model M keyboard in 1996. The Model M keyboard was designed to be less expensive to produce than the Model F keyboard it replaced. Principal design work was done at IBM in 1983–1984, drawing on a wide range of user feedback, ergonomic studies, and examination of competing products. Its key layout, significantly different from

2580-582: The AT as the best desktop computer when "price is no object" for 1984, describing it as "an innovative, state-of-the-art computer that has the competition gasping for breath". An industry analyst wrote in Computerworld in 1985 that the AT's power was evidence of IBM's belief that personal computers were more important for the company than minicomputers. On April 2, 1987, IBM announced the Personal System/2 (PS/2) line, which they marketed as

2666-550: The AT, originally a Seagate ST506 compatible interface on IBM's disk controller card, was updated and standardized as ATA ("AT Attachment") by Western Digital and Compaq in 1986, and later renamed PATA ( Parallel AT Attachment ). The ATA interface was also known as IDE, because the drive controller, instead of being on the interface card, was integrated into the drive ( Integrated Drive Electronics ). As of January 1985 AT sales were so strong that IBM and its suppliers could not keep up with demand. Creative Computing chose

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2752-550: The CPU's I/O lines. IBM referred to these as "I/O slots", but after the expansion of the PC clone industry they became retroactively known as the ISA bus . At the back of the machine is a metal panel, integrated into the steel chassis of the system unit, with a series of vertical slots lined up with each card slot. Model M keyboard The popularity of the IBM PC and its successors made

2838-491: The Corporate Management Committee, which converted the group into a business unit named "Project Chess", and provided the necessary funding and authority to do whatever was needed to develop the computer in the given timeframe. The team received permission to expand to 150 people by the end of 1980, and in one day more than 500 IBM employees called in asking to join. The design process was kept under

2924-523: The Customizer. There have been other configurations, including updated 104- and 105-key layouts; a Unix layout (where the Ctrl , Caps Lock , Esc , and tilde keys are transposed); models with integrated pointing sticks and trackballs ; and POS -specific models such as those with built-in magstripe readers. All used the press-fit controller characteristic of late Lexmarks. Unicomp continued to use

3010-510: The IBM 5150's lifecycle and only usable with dedicated software support (i.e. only accessible via a RAM window in the Upper Memory Area ); this was relatively rarely equipped and utilized on the original IBM PC, much less fully so, thus the machine's maximum RAM configuration as commonly understood was 640 KB. The BIOS is the firmware of the IBM PC, occupying one 8 KB chip on the motherboard. It provides bootstrap code and

3096-551: The IBM PC AT. In the United States, popular brands of AT clones included the Tandy 3000 , Compaq Deskpro 286, HP Vectra, Zenith Z-286, Epson Equity Models II+ and III, and Commodore PC-30 and PC-40 . In Europe, on the other hand, most AT-clones sold were more or less anonymous. The AT bus became the de facto ISA ( Industry Standard Architecture ), while PC XT slots were retroactively named 8-bit ISA . The disk interface for

3182-435: The IBM PC offered a port for connecting a cassette data recorder . Unlike the typical home computer however, this was never a major avenue for software distribution, probably because very few PCs were sold without floppy drives. The port was removed on the very next PC model, the XT. At release, IBM did not offer any hard disk drive option and adding one was difficult - the PC's stock power supply had inadequate power to run

3268-399: The IBM PC was very significant to its success in the market. Some publications highlighted IBM's uncharacteristic decision to publish complete, thorough specifications of the system bus and memory map immediately on release, with the intention of fostering a market of compatible third-party hardware and software. The motherboard includes five 62-pin card edge connectors which are connected to

3354-502: The ISA bus, a 16-bit bus with backward compatibility with 8-bit PC-compatible expansion cards. The bus also offered fifteen IRQs and seven DMA channels, expanded from eight IRQs and four DMA channels for the PC, achieved by adding another 8259A IRQ controller and another 8237A DMA controller. Some IRQ and DMA channels are used by the motherboard and not exposed on the expansion bus. Both dual IRQ and DMA chipsets are cascading which shares

3440-560: The Lexmark Select-Ease Keyboard (model M15), including a buckling-spring switch patent. They continued to manufacture the IBM Enhanced Keyboard with TrackPoint II (model M13) in Mexico until 1998. Some of Lexmark's keyboard manufacturing assets were also sold to a group of Lexmark employees, who formed Unicomp whose basic version of the Model M was similar to part number 42H1292, first renamed 42H1292U and later

3526-609: The M13, which was also built like rugged Model Ms but featured a pointing stick . The M5 and M13 designs are still carried by Unicomp in 2021 under the names Trackball Classic and Endura Pro. The variant most commonly referred to as "Model M" is Part No. 1391401, on which many other variants were based. This model, known as the Enhanced Keyboard, included IBM's patented buckling spring design and swappable keycaps. The Model M's design has been widely described as reliable, and

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3612-560: The Model F's, owed much (including notably the inverted-T arrangement of its arrow keys) to the LK-201 keyboard shipped with the VT220 serial terminal. Production of Model M keyboards began in 1985. They were often bundled with new IBM computers. While today primarily associated with the IBM PC and its successors, it actually first shipped with the 3161 terminal and was deployed across several other IBM product lines as well, notably including

3698-477: The Model M sometimes being referred to as the "clicky keyboard." Until the late fourth-generation variants, most Model Ms were manufactured with a 1.25" slotted, circular speaker grille in their bottom surfaces. Relatively few contain an actual speaker, however, which was useful only for sounding beep codes on older terminal systems. The most common P/Ns with speakers are 1394540 and 51G872, made for RS/6000 UNIX workstations. Model Ms have been manufactured to quite

3784-424: The Model M than on other keyboards. Additionally, many model M enthusiasts believe that tactile-feedback keyboards like the Model M reduce stress on the hands, preventing or even reversing repetitive strain injury . Significant pressure is required to press the keys, and a pronounced sound results to help typists previously trained on typewriters who had become accustomed to that level of feedback. This resulted in

3870-585: The Model M's design influential: Almost all later general-purpose computer keyboards mimicked its key layout and other aspects of its ergonomics. The layout was standardized by ISO in 1994 and ANSI in 1998, with minor additions—most notably the Windows key and Menu key . The Model M is regarded as a classic and durable piece of hardware. Although the computers and computer peripherals produced concurrently with them are considered obsolete, many Model M keyboards are still in use due to their physical durability and

3956-643: The PC AT architecture was functionally an open design, and IBM's efforts to trademark the AT name largely failed. Many 286-based PCs were modeled after it and marketed as AT-compatible . The label also became a standard term in reference to PCs that used the same type of power supply, case, and motherboard layout as the 5170. AT-class became a term describing any machine which supported the same BIOS functions, 80286 or greater processor, 16-bit expansion slots, keyboard interface, 1.2 MB 5 + 1 ⁄ 4 inch floppy disk drives and other defining technical features of

4042-450: The PC keyboard, but a different, bidirectional electrical interface with different keyboard scan codes . The bidirectional interface allows the computer to set the LED indicators on the keyboard, reset the keyboard, set the typematic rate, and other features. Later ATs included 101-key keyboards, e.g. the Model M keyboard . The AT is also equipped with a physical lock that prevents access to

4128-462: The PC, covering such features as the bytecoding for color monitors, DMA access operation, and the keyboard interface. They were never enforced. Many of the designers were computer hobbyists who owned their own computers, including many Apple II owners, which influenced the decisions to design the computer with an open architecture and publish technical information so others could create compatible software and expansion slot peripherals. During

4214-520: The chassis is dominated by a motherboard which houses the CPU, built-in RAM, expansion RAM sockets, and slots for expansion cards. The IBM PC was highly expandable and upgradeable, but the base factory configuration included: The PC is built around a single large circuit board called a motherboard which carries the processor, built-in RAM, expansion slots, keyboard and cassette ports, and the various peripheral integrated circuits that connected and controlled

4300-567: The components of the machine. The peripheral chips included an Intel 8259 PIC , an Intel 8237 DMA controller, and an Intel 8253 PIT . The PIT provides 18.2 Hz clock "ticks" and dynamic memory refresh timing. The CPU is an Intel 8088 , a cost-reduced form of the Intel 8086 which largely retains the 8086's internal 16-bit logic, but exposes only an 8-bit bus. The CPU is clocked at 4.77 MHz, which would eventually become an issue when clones and later PC models offered higher CPU speeds that broke compatibility with software developed for

4386-414: The computer by disabling the keyboard and holding the system unit's cover in place. ATs could be equipped with CGA , MDA , EGA , or PGA video cards. The 8250 UART from the PC was upgraded to the 16450 , but since both chips had single-byte buffers, high-speed serial communication was problematic as with the XT. The IBM PC AT came with a 192-watt switching power supply , significantly higher than

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4472-402: The continued validity of their ANSI 101-key and ISO 102-key layouts, through the use of a PS/2-female-to-USB-male adapter with a built-in interface converter. Since their original popularity, new generations have discovered their unique functionality and aesthetics. It is estimated that during the IBM and Lexmark years, over 10 million Model Ms were shipped. Their mass-market success ended in

4558-469: The design constraint to use off-the-shelf parts . The TMS9900 was rejected as it was inferior to the Intel 8088. IBM chose the 8088 over the similar but superior 8086 because Intel offered a better price for the former and could provide more units, and the 8088's 8-bit bus reduced the cost of the rest of the computer. The 8088 had the advantage that IBM already had familiarity with the 8085 from designing

4644-533: The design has not changed significantly over time. Thanks to the M's design, including its heavy steel backplate and strong plastic frame, many early Model M Keyboards are still functional four decades past release. The Model M's buckling spring key design specification gives it a unique feel and sound. Unlike more common and lower-end rubber dome designs, buckling springs give users a notable tactile and auditory feedback. Because of its more defined touch, some users report they can type faster and more accurately on

4730-534: The design process IBM avoided vertical integration as much as possible, for example choosing to license Microsoft BASIC rather than utilizing the in-house version of BASIC used for mainframes due to the better existing public familiarity with the Microsoft version. The IBM PC debuted on August 12, 1981, after a twelve-month development. Pricing started at $ 1,565 for a configuration with 16 KB RAM, Color Graphics Adapter , keyboard, and no disk drives. The price

4816-645: The direct replacement for the AT for customers who wanted to buy a true IBM system. IBM Personal Computer The IBM Personal Computer (model 5150, commonly known as the IBM PC ) is the first microcomputer released in the IBM PC model line and the basis for the IBM PC compatible de facto standard . Released on August 12, 1981, it was created by a team of engineers and designers at International Business Machines (IBM), directed by William C. Lowe and Philip Don Estridge in Boca Raton, Florida . Powered by an x86 -architecture Intel 8088 processor,

4902-401: The diskette would be problematic. Conversely, the high-density drive's heads had a track width half that of the 360 KB drive, so they were incapable of fully erasing and overwriting tracks written by a 360 KB drive. Overwriting a DD disk that had been written in a DD drive with an HD drive would result in a disk that read on an HD drive, but produced read errors in a DD drive. Whereas

4988-533: The form of the PS/2 Model 30 , the AT did not. Users either had to forgo all their 16-bit ISA expansion cards and switch to the proprietary Micro Channel architecture , or settle for a clone if they wanted to upgrade their machine while keeping their expansions. Eventually, in September 1988, IBM announced the PS/2 Model 30 286 , which featured an Intel 80286 processor and 16-bit ISA expansion slots, serving as

5074-450: The keyboard was extremely positive, with some sources describing it as a major selling point of the PC and even as "the best keyboard available on any microcomputer." At release, IBM provided a Game Control Adapter which offered a 15-pin port intended for the connection of up to two joysticks, each having two analog axes and two buttons. (The early PCs predated the advent of the " Windows, Icons, Mouse, Pointer" concept and so did not have

5160-411: The latter provided medium- and low-resolution color graphics and text. CGA used the same scan rate as NTSC television , allowing it to provide a composite video output which could be used with any compatible television or composite monitor , as well as a direct-drive TTL output suitable for use with any RGBI monitor using an NTSC scan rate. IBM also sold the 5153 color monitor for this purpose, but it

5246-407: The machine was based on open architecture and third-party peripherals. Over time, expansion cards and software technology increased to support it. The PC had a substantial influence on the personal computer market ; the specifications of the IBM PC became one of the most popular computer design standards in the world. The only significant competition it faced from a non-compatible platform throughout

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5332-456: The manufacturing label, if present, says "M2" rather than "M." M2s were poorly fabricated and notoriously unreliable; comparatively few survived into the 21st century, and Model M enthusiasts do not value them. The M2 should in turn be distinguished from the M5, another Lexmark variant which returned to the rugged Model M case/backplate construction but added a built-in trackball ; and those two from

5418-554: The market, rumors of clones began, and the first legal PC-compatible clone—the MPC 1600 by Columbia Data Products —was released in June 1982, less than a year after the PC's debut. Eventually, IBM sold its PC business to Lenovo in 2004 . For low cost and a quick design turnaround time, the hardware design of the IBM PC used entirely "off-the-shelf" parts from third party manufacturers, rather than unique hardware designed by IBM. The PC

5504-515: The market, sold only 69,000. Software support from the industry grew rapidly, with the IBM nearly instantly becoming the primary target for most microcomputer software development. One publication counted 753 software packages available a year after the PC's release, four times as many as were available for the Macintosh a year after its launch. Hardware support also grew rapidly, with 30–40 companies competing to sell memory expansion cards within

5590-549: The more common buckling-spring variants. A five-year agreement obligating IBM to purchase nearly all of its keyboards from Lexmark expired on March 27, 1996. Lexmark exited the keyboard business, selling related assets to IBM and Maxi Switch. When Lexmark discontinued keyboard production in April 1996, IBM continued producing buckling-spring Model M's in Scotland until 1999. Maxi Switch purchased assets for rubber-dome keyboards and

5676-622: The more sought after variants of the Model M keyboard is the Space Saving Keyboard, which integrates the number pad into the keyboard's main section, substantially reducing its width. The Space Saving Keyboard is likely the origin of the keyboard layout that is generally known as a "Tenkeyless keyboard." IBM released the standard and Space Saving Model M's in an alternative 'gray/pebble' color for use with their Industrial computers, designed to conceal discoloration from handling in production environments. Other variable features include

5762-567: The most obvious use was the addition of an Intel 8087 math coprocessor, which improved floating-point math performance. PC mainboards were manufactured with the first memory bank of initially Mostek 4116-compatible, or later 4164-compatible DIP DRAMs soldered to the board, for a minimum configuration of first just 16 KB, or later 64 KB of RAM. Memory upgrades were provided by IBM and third parties both for socketed installation in three further onboard banks, and as ISA expansion cards. The early 16 KB mainboards could be upgraded to

5848-415: The new product. Reception was overwhelmingly positive, with analysts estimating sales volume in the billions of dollars in the first few years after release. After release, IBM's PC immediately became the talk of the entire computing industry. Dealers were overwhelmed with orders, including customers offering pre-payment for machines with no guaranteed delivery date. By the time the machine began shipping,

5934-422: The next four years, cost pressure led to several minor design changes intended to lower the part and fabrication costs of Lexmark Model Ms. The case and metal backplate were repeatedly lightened. The cable jack and detachable SDL cable were replaced with a fixed cable. Some variants were made with a single color for key legends. In 1995 Lexmark made the most sweeping design change in the Model M's history, altering

6020-653: The original IBM machinery to produce Model Ms, leading to a gradual decline in quality as the tooling became worn. This, and various problems with their USB controllers helped keep a market for vintage Model Ms thriving. In 2020 Unicomp replaced its tooling and shipped a "New Model M" with noticeably improved build quality that more closely resembles the classic 1391401 (though with a 104- or 103-key layout and USB); many older variants are no longer sold on Unicomp's website and some still on sale have been deprecated. The Model M's numerous variations (referred to as "part numbers") incorporated alternative features and/or colors. One of

6106-503: The original PC. The single base clock frequency for the system was 14.31818 MHz, which when divided by 3, yielded the 4.77 MHz for the CPU (which was considered close enough to the then 5 MHz limit of the 8088), and when divided by 4, yielded the required 3.579545 MHz for the NTSC color carrier frequency. The PC motherboard included a second, empty socket, described by IBM simply as an "auxiliary processor socket", although

6192-644: The place of the DIP switches used to set system settings on PCs. Most AT clones have the setup program in ROM rather than on disk. The standard floppy drive was upgraded to a 1.2 MB 5 + 1 ⁄ 4  inch floppy disk drive (15 sectors of 512 bytes, 80 tracks, two sides), which stored over three times as much data as the 360 KB PC floppy disk, but had compatibility problems with 360k disks (see Problems below). 3 + 1 ⁄ 2  inch floppy drives became available in later ATs. A 20 MB hard disk drive

6278-438: The primary pair. In addition to these chipsets, Intel 82284 Clock Driver and Ready Interface and Intel 82288 Bus Controller are to support the microprocessor. The 24-bit address bus of the 286 expands RAM capacity to 16  MB . PC DOS 3.0 was included with support for the new AT features, including preliminary kernel support for networking (which was fully supported in a later version 3.x release). The motherboard includes

6364-447: The reason for the decision to use third-party components. Atari proposed to IBM in 1980 that it act as original equipment manufacturer for an IBM microcomputer, a potential solution to IBM's known inability to move quickly to meet a rapidly changing market. The idea of acquiring Atari was considered but rejected in favor of a proposal by Lowe that by forming an independent internal working group and abandoning all traditional IBM methods,

6450-563: The second-generation of IBM PC. The company promised to continue manufacturing certain models of the first-generation PC, including the AT, for the coming months. In June 1987, they announced the full withdrawal of the PC/XT and the imminent discontinuation of the PC/AT. The last units of PC/AT (model 339) rolled off the assembly line in July. While the PC/XT received a directly compatible replacement in

6536-428: The size and location of the internal controller board. While the new "press-fit" design successfully lowered manufacturing costs by eliminating the two ribbon cables and separate LED daughterboard of older versions, the controller's new card-edge connector proved to be a failure point that shortened the keyboard's average lifetime. The classic era of the Model M is generally considered to have ended with this change, though

6622-407: The term "PC" was becoming a household name. Sales exceeded IBM's expectations by as much as 800% (9x), with the company at one point shipping as many as 40,000 PCs per month. IBM estimated that home users made up 50 to 70% of purchases from retail stores. In 1983, IBM sold more than 750,000 machines, while Digital Equipment Corporation , one of the companies whose success had spurred IBM to enter

6708-481: The term as Advanced Technology , including at least one internal IBM document. IBM 's 1984 introduction of the AT was seen as an unusual move for the company, which typically waited for competitors to release new products before producing its own models. At $ 4,000–6,000, it was only slightly more expensive than considerably slower IBM models. The announcement surprised rival executives, who admitted that matching IBM's prices would be difficult. No major competitor showed

6794-567: The value of entering this growing market, assigned William C. Lowe and Philip Don Estridge as heads of the new Entry Level Systems unit in Boca Raton, Florida. Market research found that computer dealers were very interested in selling an IBM product, but they insisted the company use a design based on standard parts, not IBM-designed ones so that stores could perform their own repairs rather than requiring customers to send machines back to IBM for service. Another source cites time pressure as

6880-402: Was designed to compete with comparable machines in the market. For comparison, the Datamaster, announced two weeks earlier as IBM's least expensive computer, cost $ 10,000. IBM's marketing campaign licensed the likeness of Charlie Chaplin 's character " The Little Tramp " for a series of advertisements based on Chaplin's movies, played by Billy Scudder. The PC was IBM's first attempt to sell

6966-406: Was essentially complete by April 1981, when it was handed off to the manufacturing team. PCs were assembled in an IBM plant in Boca Raton, with components made at various IBM and third party factories. The monitor was an existing design from IBM Japan ; the printer was manufactured by Epson . Because none of the functional components were designed by IBM, they obtained only a handful of patents on

7052-462: Was included as standard. Early drives were manufactured by Computer Memories and were found to be very unreliable. The AT included the AT keyboard , initially a new 84-key layout (the 84th key being SysRq ). The numerical keypad was now clearly separated from the main key group, and indicator LEDs were added for Caps Lock, Scroll Lock and Num Lock. The AT keyboard uses the same 5-pin DIN connector as

7138-540: Was initially developed for the IBM Datamaster , and was substantially better than the keyboards provided with virtually all home computers on the market at that time in many regards - number of keys, reliability and ergonomics. While some home computers of the time utilized chiclet keyboards or inexpensive mechanical designs, the IBM keyboard provided good ergonomics, reliable and positive tactile key mechanisms and flip-up feet to adjust its angle. Public reception of

7224-423: Was large enough for IBM's attention, with $ 15 billion in sales by 1979 and projected annual growth of more than 40% during the early 1980s. Other large technology companies had entered it, such as Hewlett-Packard , Texas Instruments and Data General , and some large IBM customers were buying Apples. As early as 1980 there were rumors of IBM developing a personal computer, possibly a miniaturized version of

7310-420: Was no way for the disk drive to detect what kind of floppy disk was inserted, and the drives were not distinguished except by an asterisk molded into the 360 KB disk drive faceplate. If the user accidentally used a high-density diskette in the 360 KB drive, it would sometimes work, for a while, but the high- coercivity oxide would take a very weak magnetization from the 360 KB write heads, so reading

7396-453: Was not available at release and was not released until March 1983. MDA scanned at a higher frequency and required a proprietary monitor, the IBM 5151 . The card also included a built-in printer port. Both cards could also be installed simultaneously for mixed graphics and text applications. For instance, AutoCAD , Lotus 1-2-3 and other software allowed use of a CGA Monitor for graphics and

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