Processor that trades potential performance for backward compatibility with dinosaur programs. Apparently Intel feels there is something wrong with having a few people simply recompile code. If they streamlined everything, it would be killer speed. Instead it wastes CPU cycles on CISC code and managing the stone-age ISA bus. (although I must confess, my modem is ISA, due to all the PCI shit being winmodems and all)

I wonder how much of an improvement IA-64 really is. Probably much more bloated than the current x86's.

Zorin: Nice. It should be noted that the Pentium Pro up to Pentium III are all the same processor family: i686.

The Intel manufactured processors in the x86 line:

  • i8088 - 16 bit processor. Started the line. Had an 8 bit external bus to reduce cost. Oddly enough, many were manufactured by future competitor AMD.
  • i8086 - 16 bit processor. Started the line. Had a full 16 bit external bus. Not used much in PC's.
  • i80286 - 16 bit processor. Introduced the 286 protected mode, which failed because it was rather clunky.
  • i80386(DX) - Intel's first true 32 bit processor. Introduced 386 protected mode, which had all the proper memory management features any full fledged CPU should have. The "DX" nomenclature was tacked on when the 386SX (see below) was introduced.
  • i80386SX - Identical to the 386 in function, but had a 16 bit external bus. This saved money on lower end systems.
  • i80486(DX) - Basically, a 386 with a few extra instructions and an onboard cache. This cache improved performance vastly. It also integrated the x87 math coprocessor into the CPU for the first time. The "DX" nomenclature was tacked on when the 486SX (see below) was introduced.
  • i80486SX - A 486 with a broken or disabled math coprocessor.
  • Pentium Classic, or just plain "Pentium" - Intel's first x86 chip to use multiple instruction pipelines.
  • Pentium Pro - A slightly improved Pentium which has a large in-package L2 cache. Cache and core ran at the same speed. Failed due to high production costs- if the cache chip OR the die were bad, the whole thing had to be junked.
  • Pentium MMX - Added the MMX instruction set to the Pentium Classic processor. All Intel CPU's from this point on have MMX instructions available.
  • Pentium II - The answer to the Pentium Pro cache problem: two separate packages on a PC board that plugs into a slot, known as Slot One.
  • Pentium Xeon processors - Improved versions of the Pentium II, III, and 4, containing larger caches, and the ability to use more than two (or in the case of Pentium 4, one) processors in SMP mode. Intended to be used in servers.
  • Celeron - A name for any number of stripped down Pentium II or III chips. Usually they lack cache, or run at a slower front side bus speed.
  • Pentium III Katmai - Improved Pentium II. Has some extra instructions and runs at higher clock speeds.
  • Pentium III Coppermine - An improved version of the Pentium III that has an on-die 256K cache and runs at higher clock speeds. Contrary to its name, it does not actually use copper interconnect technology.
  • Pentium M - Mobile processor, based on the Pentium III with power saving tweaks. Actually does more work per clock-cycle than the Pentium 4, and requires less cooling, which has led to some people using it in fanless desktop systems.
  • Pentium 4 - A partial redesign of the Pentium III, simplified in some aspects so that it can run at higher clock speeds. This is a marketing gimmick, of course; the CPU can run at around 3GHz but it doesn't do nearly as much per clock cycle as the older Pentium III.

The line starts to blur as you get into the Pentium II/III and Celeron series. There are many different versions of the Celeron, Pentium III, and so on. Please note that this list is in vague order of introduction; the "DX" versions of the 386 and 486 came before the "SX" versions. Also, /msg me if you find any errors.

This is a timeline of milestones in the history Intel Microprocessors. Just listed are the first models, as Intel usually releases updated models with improved clock speeds within a few years of a line's initial launch.

  • i8088 - February 1978
  • i8086 - June 8, 1978
  • i80286 - February 1982
  • i80386DX - October 17, 1985
  • i80386SX - June 16, 1988
  • i80486DX - April 10, 1989
  • i80486SX - April 22, 1991
  • Pentium Classic 60/66 MHz - March 23, 1993
  • Pentium Pro (200, 180, 166, 150 MHz) - November 1, 1995
  • Pentium MMX (200, 166 MHz) - January 8, 1997
  • Pentium II (300, 266, 233 MHz) - May 7, 1997
  • Mobile Pentium MMX (200/233 MHz) - September 8, 1997
  • Mobile Pentium II (233/266 MHz) - April 2, 1998
  • Celeron 266 MHz - April 15, 1998
  • Pentium II Xeon 400 MHz - June 29, 1998
  • Pentium III (450, 500, 550, and 600MHz) - February 26, 1999
  • Pentium III Xeon 500/550 MHz - March 17, 1999
  • Mobile Celeron 333 MHz - April 5, 1999
  • Mobile Pentium III 400/450/500 MHz - Oct. 25, 1999
  • Pentium 4 1.4/1.5 GHz - November 20, 2000
x86 is both the generic name given to the family of microprocessors based upon (and backwards compatible with) the Intel 8086, and the instruction set architecture (ISA) implemented by these CPUs. The x86 ISA has been extended many times over the years and today barely resembles the 16-bit architecture introduced in 1978. It is by far the most dominant ISA for personal computers, and has also made inroads in the areas of high-performance computing and embedded systems. 

The initial success of x86 was tied to its use in the original IBM PC 5150 in the form of the Intel 8088.  The unexpected success of the IBM PC and its eventual series of (compatible) imitators brought the 8088 and its ISA along with them, establishing x86 as one of the prominent microcomputer architectures of the 1980s. Its main competition came in the form of the Motorola 68000 and its successors, whose minicomputer-derived architecture was widely considered to be superior to x86 and its descent from the grubby 8-bit processor architectures of the 1970s. The 68000 architecture would go on to power the main competitors to the PC architecture, including the Macintosh and the Amiga, until its replacement by PowerPC in the early 1990s.

In the end, what powered x86 past its competition was not any intrinsic advantage in the processor itself, but the PC-AT system architecture and its accompanying MS-DOS and Windows operating systems. The freely-available hardware specifications and promiscuously-licensed OS fueled a broad, competitive hardware marketplace that drove prices down and availability up, regardless (and often despite) the limitations of the 8088 and successor 80286 processor architectures, that the single-vendor competitor systems ultimately could not keep up with. 

The x86 architecture was updated to overcome many of these limitations with the introduction of the Intel 80386 in 1986. The 386 extended the ISA to 32 bits and, in 32-bit, backwards incompatible mode, did away with several of the most egregious limitations of the original x86 ISA. Most important of these was the awkward memory addressing system of the 8088 and 80286, familiar to MS-DOS users through the distinctions between 'conventional memory', 'expanded memory', and 'extended memory'. 32-bit mode replaced this with a straightforward 'flat' address space similar to the 68000. Though coprocessors for floating point math had been available since the early days of the PC, the 386 era saw the math coprocessor become much more common; with its integration on to the main CPU with the 486, these 'x87' coprocessors added their own (ugly) instructions to the x86 architecture.

With a power struggle over the replacement of the ISA system bus removing IBM from central guidance of the PC architecture and the death of all competitors except the now PowerPC-based Apple Macintosh, the x86 architecture consolidated its hold on the general computing market in the early 1990s. The rising Windows operating system carried x86 with it wherever it went, despite ports of Windows NT to PowerPC and Alpha machines, and with IBM no longer the central touchstone of new PC hardware, Intel became the face of the core PC architecture. The seeming double monopoly of Intel on the hardware side and Microsoft on the software side led the PC platform to be redubbed 'Wintel', a term used equally as a neutral description by its proponents and as a derogatory term by its detractors.

The continuing ugliness of x86 and unreliability of Windows led many to predict/hope for a new, more modern platform to supplant the Wintel hegemony. By this point, x86 was the only processor architecture remaining from before the 'RISC revolution', where it was found that simplifying the set of processor instructions allowed better hardware and software efficiency. Aesthetically, the RISC designs that competed with x86, with their 'less is more' philosophy, were much better embodiments of good engineering practice and thus deserved to win the day.

However, x86 processors were re-architected to benefit from the strength of RISC processor design, scrapping the original micro-architecture for the combination of a RISC-like execution core with a translation unit that converts the ugly CISC x86 instruction stream into a series of clean, simple RISC-style instructions. This allows the ugliness of the x86 instruction set to only have a constant effect on the overall performance of the processor, rather than requiring the main processor core to be complicated by its requirements. This constant penalty was originally quite large, but as Moore's Law has provided ever greater amounts of computing power, it has dwindled to near meaninglessness. 

The Wintel core in the otherwise highly-competitive PC marketplace was broken in the late 1990s and early 2000s. In 1999 AMD, a longtime manufacturer of Intel-compatible processors, released the original Athlon, an x86-compatible processor comparable, for the first time, with Intel's best and most expensive processors. The Athlon entered a long period of competition with Intel's Pentium III and later Pentium 4 processors, with the end result that AMD was comfortable introducing the next major step for the x86 ISA: x86-64, which extends the ISA to 64 bits while eliminating more of its limitations.

In the meantime, the upstart Linux operating system had mostly destroyed the older proprietary UNIX systems and has now been positioned as the strongest competition to Windows on its own hardware platform. Also, in 2006, Apple abandoned PowerPC and rebuilt the Macintosh on top of a PC-architecture Intel-based machine. While the Mac OS will still only run on custom Apple hardware, it is a testament to the power of the commodity x86 architecture that the Mac made the difficult transition.

Overall, the focus on backwards compatibility in both hardware and software has allowed x86 to become the standard architecture that it has. Change in the computer market, despite the manifold claims of computer companies, is generally gradual, with backward compatibility at every stage allowing people to adopt the new without discarding the old. This is true for both hardware, where the ISA bus lived long past its replacement by PCI, and in the world of proprietary software, where simple recompilation for a new architecture just isn't so simple. The PC architecture and the x86 processor at its core have evolved into something vastly different than they were initially, while retaining backward compatibility so that old hardware and software can be kept, if not forever, then at least for a little longer. Having now defeated all competition in the personal computer market, x86 is now moving up to challenge SPARC and Itanium in large-scale server, and also down to challenge the ubiquitous ARM microcontrollers in the embedded device market.

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