IBM Personal Computer

IBM Personal Computer (Eng. " personal computer ", short IBM PC) was the model name of the first personal computer (PC ) of the U.S. company IBM in the year 1981. Meanwhile successor models had the same name, by the name of additives such as XT and AT. The product line was a great commercial success for IBM, the company is thus an informal, worldwide industry standard and defined the current device class until today, the personal computer. The numerous imitations and continuations of IBM PCs were designated as IBM - PC compatible computers by other companies. Today's market PCs with Windows operating system and x86 processors based on the continuous development of the former concept.

The first IBM personal computer had no hard disk, but only one or two floppy drives, he wore the internal name IBM model 5150 and was built from 1981 to almost six years unchanged. Follow-up systems with hard disk called themselves IBM Personal Computer XT and later, with an Intel 80286 processor, IBM Personal Computer / AT. After the unfortunate introduction of the hardware side is not PC compatible personal System/2-Modelle by IBM and with the release of Microsoft Windows 3.0, the term " IBM PC" was already in 1990 a more historical term. Since the introduction of Microsoft Windows 95 was in the PC market segment practically only of Windows compatibility spoken.


The IBM model 5150 came on 12 August 1981 to the market and had been developed quickly in order not to leave the currently rapidly growing market for microcomputers of the competition - especially the Apple II Until that time, IBM had only intended solely for commercial customer specific systems IBM System/32 5100 and produced. However, these were not comparable with the much cheaper and more flexible systems such as the Apple II.

Although the development of the IBM PC was carried out in the shortest possible time and using the cheapest available components (see commercial off -the-shelf ), he was a complete success. One of the biggest advantages was that he was just like the original Apple II by cards that could be retrofitted to the computer, expandable. The basic configuration in the United States for U.S. $ 3,000 ( according to current purchasing power about 8,000 U.S. dollars) in the Federal Republic for 8500 D- Mark ( according to today's purchasing power approximately 8,600 euros ) was offered, had no hard drive, but only one or two disk drives. Moreover, caused by the simple structure of the PCs for everyone standard chips readily available already in 1983 in the Far East several replicas (often wrongly because inaccurate, IBM clone called ), which ensured a wide dissemination of the system architecture. The IBM PC quickly became an unofficial industry standard because it could be rebuilt without licensing by IBM. Even the operating system of the IBM PC, DOS 1.0, IBM did not have complete control, because it was originally developed by Microsoft.

The term IBM PC shaped the conception of what is a PC. From the mid- 1980s, PCs were not IBM-compatible, except in the home computer sector simply not for sale. For the promised feature " IBM - compatible " manufacturers of replicas of an IBM PC there was never official tests or certifications. As a criterion often served a compatibility test with the simulator program from Microsoft. This appealed to the then-common hardware from to their limits and reached as deep on BIOS functions that it could only be used with a 100% compatible BIOS.

In the later years, IBM had no lucky hand in developing the IBM PC. While at IBM, using proprietary concepts (eg IBM PS/2-Computern and its Micro Channel Architecture or OS / 2) tried to close the market to competitors, developed manufacturers such as Compaq, HP, Intel and Microsoft more sustainable concepts and cross-vendor standards (eg, Extended Industry Standard Architecture ), and could with their market power this - unlike IBM - prevail as industry standards. Only in the business sector and in specific sectors such as the banking sector, the IBM PS/2-Modelle could - actually intended as the successor of all PCs - keep a few years relatively successful. Then you failed but - apparently the delimitation came to competitors due to the change of the bus system used on the license fee-based " IBM microchannel " architecture works too well.

Even today, PCs based on x86 processors from Intel or AMD largely compatible with its ancestor, the IBM PC, even if the attribute " IBM - compatible " is a very long time is no longer advertised.

System Architecture / Technical design

The processor was used the 16 -bit processor 8088 from Intel, a version of the 8086 with an external 8- bit data bus. The CPU was clocked at 4.77 MHz, which is 4/3mal the color carrier frequency of the NTSC color television system, as first television sets were provided as monitors as in the home computers. With the same clock rate and the 8-bit ran wide system, which was standardized later in its introduced with the IBM PC / AT 16 -bit version called the ISA bus.

The device was initially delivered after his performance with either 16 or 64 KB of memory, with a further developed motherboard then later with up to 256 KB. A coprocessor for fast floating point was included in the system design. This block, called 8087 was subsequently inserted into an empty socket. The main memory on the motherboard itself could - depending on the version of the selfsame - be extended to up to 64 or 256 KB, through third-party plug- later even up to 640 KB. Although the processor itself was able to address 1024KB, system design but generous 384 KB of address space for other purposes were provided, for example for the BIOS and the graphics memory.

The PC could initially be equipped with one or two 5.25 " floppy drives. An optional extension housing two floppy drives were connected, although this is more of a theoretical possibility because of the then high price of drive components. The floppy drives were for single- writable disks with a capacity of 160 KB or double-sided floppy disk of 320 KB will be used later even 360K.

Later it was the 5150 can also be equipped with a hard disk with a capacity of 10 MB. These were for a 5.25 "drive with MFM recording and full-height, ie twice the height of a conventional DVD drive today. Unlike the successor system PC XT also has connection for a data recorder was available, as it was common for home computers.

Expansion unit

The PC could be 5161 ( Expansion Unit ) enlarge an identical case with space for extra drives and expansion cards with the Expansion Unit Model. For this purpose, a card with driver modules is plugged into the PC, with the connecting the bus of the PC expansion unit via a cable.

Other models in the series