Influence of the IBM PC on the personal computer market

The IBM Personal Computer (model 5150)

Following the introduction of the IBM Personal Computer, or IBM PC, many other personal computer architectures became extinct within just a few years.

Before the IBM PC's introduction

Before the IBM PC was introduced, the personal computer market was dominated by systems using the 6502 and Z80 8-bit microprocessors, such as the TRS 80 and Apple II series, which used proprietary operating systems, and by computers running CP/M.

Around 1978, several 16-bit CPUs became available. Examples included the Data General Mn601, Fairchild's 9440, the Ferranti F100-1, the General Instrument CP1600 and CP1610, the National Semiconductor INS8900, Panafacom's MN1610, Texas Instruments' TMS9900, and, most notably, the Intel 8086. These new processors were expensive to incorporate in personal computers, as they used a 16-bit data bus and needed rare (and thus expensive) 16-bit peripheral and support chips.

Business-oriented personal computers before the IBM PC

More than 50 new business-oriented personal computer systems came on the market in the year before IBM released the IBM PC. Very few of them used a 16- or 32-bit microprocessor, as 8-bit systems were generally believed by the vendors to be perfectly adequate, and the Intel 8086 was too expensive to use.

Some of the more important manufacturers selling 8-bit business systems during this period were

• Apple Computer Inc.
• Commodore International
• Cromemco
• Digital Equipment Corporation
• Hewlett-Packard
• Intersystems
• Morrow Designs
• North Star Computers
• Ohio Scientific
• Olivetti
• Processor Technology
• Sharp
• South West Technical Products Corporation
• Tandy Corporation
• Zenith/Heathkit.

The IBM PC

On August 12, 1981, IBM released the IBM Personal Computer. The IBM PC used the then-new Intel 8088 processor. Like other 16-bit CPUs, it could access up to 1 megabyte of RAM, but it used an 8-bit-wide data bus to memory and peripherals. This design allowed use of the large, readily available, and relatively inexpensive family of 8-bit-compatible support chips. IBM decided to use the Intel 8088 after first considering the Motorola 68000 and the Intel i8086, because the other two were considered to be too powerful for their needs. IBM's reputation in business computing, combined with a rapid marketplace of third-party peripherals and the later introduction of IBM PC compatibles from other vendors, allowed the IBM PC architecture to take a substantial market share of business applications.

Many other companies at the time were also making "business personal computers" using their own proprietary designs, some still using 8-bit microprocessors. The ones that used Intel x86 processors often used MS-DOS or CP/M-86, just as 8-bit systems with an Intel 8080 compatible CPU normally used CP/M.

The use of MS-DOS on non IBM PC compatible x86 based systems

In the beginning, when the IBM PC did not yet dominate the market, these x86-based systems were not clones of the IBM PC design, but had different internal designs, like the CP/M-based 8-bit systems that preceded them. Even a few years after the IBM PC's introduction, manufacturers such as Digital, HP, Sanyo, Tandy, Texas Instruments, Tulip Computers, NEC, Wang Laboratories, and Xerox continued to introduce personal computers that were barely, if at all, hardware-compatible with the IBM PC, even though they used x86 processors and ran MS-DOS. They used MS-DOS the way Microsoft had originally envisioned: in the same way as 8-bits systems used CP/M. They implemented standard ROM BIOS routines to achieve hardware independence as had 8080 (Z80) compatibles. So each machine had a different BIOS that, as long as software made only standard MS-DOS calls, would ensure compatibility.

But to get the best results out of the 8088's modest performance, many popular software applications were written specifically for the IBM PC. The developers of these programs opted to write directly to the computer's (video) memory and peripheral chips, bypassing MS-DOS and the BIOS. For example, a program might directly update the video refresh memory, instead of using MS-DOS calls and device drivers to alter the appearance of the screen. Many notable software packages, such as the spreadsheet program Lotus 1-2-3, and Microsoft's Microsoft Flight Simulator 1.0, directly accessed the IBM PC's hardware, bypassing the BIOS, and therefore did not work on computers that were even trivially different from the IBM PC. This was especially common among games. As a result, the systems that were not fully IBM PC-compatible couldn't run this software, and quickly became obsolete, and with them the concept of OEM versions of MS-DOS meant to run (through BIOS calls) on non IBM-PC hardware. One of the first computers to use a near-clone of the IBM PC BIOS and achieve 100% compatibility was the Compaq portable, released in November 1982. Soon after Phoenix Technologies launched their clone of the IBM PC's BIOS and licensed it, which along with IBM's use of standard off-the-shelf ICs made it possible for anyone to develop a PC compatible computer.

Although based on the i8086 and enabling the creation of relatively low cost x86 based systems, the Intel 80186 quickly lost appeal for x86 based PC builders because the supporting circuitry inside the Intel 80186 chip was incompatible with those used in the standard PC chipset as implemented by IBM. It was very rarely used in personal computers after 1982.

Domination of the clones

Within a few years of the introduction of fully compatible IBM PC clones, virtually all the rival business personal computer systems, and alternate x86 using architectures, were gone from the market. Despite the inherent dangers of an industry based on a de-facto "standard", a thriving PC clone industry emerged. The only non-IBM PC-compatible systems that remained were those systems that were classified as home computers, such as the Apple II series made by Apple Inc., or business systems that offered features not available on the IBM PC, such as a high level of integration (e.g., bundled accounting and inventory) or fault-tolerance and multitasking and multi-user features.

IBM tried to capture the remaining home-computer market with the IBM PCjr, which they announced in November 1983, but did not ship until March 1984. The PCjr flopped. The remaining home computers, such as the Commodore Amiga, Atari ST, and various MSX2 computers remained on the market until IBM PC compatibles gained sufficient multimedia capabilities to compete with home computers. With the advent of inexpensive versions of the VGA video card and the Sound Blaster sound card (and its clones), most of the remaining home computers were driven from the market.

By 1995, almost no new consumer-oriented systems were released that were not IBM PC clones. Apple's Macintosh remained the sole competitive holdout. The Macintosh originally used Motorola's 68000 family of processors, later migrating to the PowerPC architecture. Throughout the 1990s Apple would steadily transition the Macintosh platform from proprietary expansion interfaces to use emerging industry standards such as IDE, PCI and USB. In 2006, Apple transitioned the Macintosh to the Intel x86 architecture. Modern Macintosh computers are essentially IBM PC compatibles, capable of booting Microsoft Windows and running most IBM PC-compatible software, but still retain unique design elements that support Apple's Mac OS X operating system.

Systems launched shortly after the IBM PC

Shortly after the IBM PC was released, a obvious split appeared between systems that opted to use an x86-compatible processor, and those that chose another architecture. Almost all of the x86 systems provided a version of MS-DOS. The others used many different operating systems, although the Z80-based systems typically offered a version of CP/M. The common usage of MS-DOS unified the x86-based systems, promoting growth of the x86/MS-DOS "ecosystem."

As the non-x86 architectures died off, and x86 systems standardized into fully IBM PC compatible clones, a market filled with dozens of different competing systems was reduced to a near-monoculture of IBM PC compatible, MS-DOS compatible systems.

x86-based systems (using OEM-specific versions of MS-DOS)

Early after the launch of the IBM PC in 1981, there were still dozens of systems that were not IBM PC-compatible, but did use Intel x86 chips. They used Intel 8088, 8086, or 80186 processors, and almost without exception offered an OEM version of MS-DOS (as opposed to the OEM version customized for IBM's use). However, they generally made no attempt to copy the IBM PC's architecture, so these machines had different I/O addresses, a different system bus, different video controllers, and other differences from the original IBM PC. These differences, which were sometimes rather minor, were used to improve upon the IBM PC's design, but as a result of the differences, software that directly manipulated the hardware would not run correctly. In most cases, the x86-based systems that didn't use a fully IBM PC compatible design didn't sell well enough to attract support from software manufacturers, though a few computer manufacturers arranged for compatible versions of popular applications to be developed and sold specifically for their machines.

Fully IBM PC-compatible clones appeared on the market shortly thereafter, as the advantages of cloning became impossible to ignore. But before that some of the more notable systems that were x86-compatible, but not real clones, were:

• the ACT Apricot by ACT
• the Dulmont Magnum
• the Epson QX-16
• the Seequa Chameleon
• the HP-150 by Hewlett-Packard and the later HP 95LX, HP 100LX, HP 200LX, HP 1000CX, HP OmniGo 700LX, HP OmniGo 100, and HP OmniGo 120.
• the Hyperion by Infotech Cie used its own H-DOS OEM version of MS-DOS
• the MBC-550 by Sanyo
• the 80186 based Mindset graphics computer
• the Morrow Designs' Morrow Pivot
• the MZ-5500 by Sharp
• the Decision Mate V from NCR Corporation; its version of MS-DOS was called NCR-DOS
• the MikroMikko_2 by Nokia
• the The NorthStar Advantage
• the PC-9800 system from NEC
• the Rainbow 100 from DEC
• the RM Nimbus by RM plc
• the Tandy/Radio Shack TRS-80 Model 2000
• the Texas Instruments TI Professional
• the Torch Graduate by Torch Computers
• the Tulip System-1 by Tulip
• the Victor 9000 by Sirius Systems Technology
• the :YES by Philips was late on the market, ran DOS Plus and MS-DOS, but by using a 80186 it was incompatible with IBM's PC
• the Z-100 by Zenith with an MS-DOS OEM version named Z-DOS

Non-x86-based systems

Not all manufacturers immediately switched to the Intel x86 microprocessor family and MS-DOS. A few companies continued releasing systems based on non-Intel architectures.

Some of these systems used a 32-bit microprocessor, the most popular being the Motorola 68000. Others continued to use 8-bit microprocessors. Many of these systems were eventually forced out of the market by the onslaught of the IBM PC clones, although their architectures may have had superior capabilities, especially in the area of multimedia. The PC architectures of that era often only had a CGA display, and no other sound system than the internal PC speaker.

Three systems of this era, while now extinct, have thriving legacies:

• The Apple Lisa by Apple Inc. was the predecessor of the Apple Macintosh, inspiring the Macintosh's design. The original Macintosh used a Motorola 68000 chip like the Lisa, and had a sufficiently similar design that some Lisa systems were converted for sale as "Macintosh XL" computers.
• The Acorn Computers Acorn Archimedes, later named the Risc PC, used a custom-designed microprocessor: the ARM. The ARM architecture continues to be popular, appearing in nearly all mobile phones and in many hand-held devices like Apple's iPhone, iPod and iPad, as well as small UNIX-based systems. The Risc PC's descendants include the A9home, the Iyonix PC and the RiscStation R7500.
• The Sun Microsystems Sun-1 and Sun-2 families of UNIX systems introduced the SunOS UNIX operating system, running on Motorola 680x0 chips. Sun's current large-scale UNIX systems use the SPARC processor family developed by Sun, but run a descendant of SunOS called Solaris.

Other non-x86-based systems included:

• the Apple IIGS, a 16-bit version of the Apple II series, with extended multimedia capabilities.
• the Commodore Amiga
• the Amstrad PCW series
• the Atari ST
• the Cromemco C-10
• Intertec's Compustar II VPU Model 20
• the Corvus Concept
• the Kaypro 10
• the Fujitsu Micro 16s
• the Micro Decision by Morrow Designs
• the MTU-130 by Micro Technology Unlimited
• the PC-9801 system from NEC
• the Xerox 820
• the Epson QX-10
• the RoadRunner from MicroOffice
• the SGI IRIS series of graphics workstations
• the TRS-80 model 16, 16e and 6000 by Tandy Corporation.

See also

• Open architecture
• Comparison of x86 DOS operating systems
• Wintel
• PC-DOS
• History of computing hardware (1960s–present)
• IBM PC compatible
• List of machines running CP/M

External links

• Dedicated to the preservation and restoration of the IBM 5150 personal computer
• OLD-COMPUTERS.COM : The Museum