Other manufacturers, such as AMD, VIA Cyrix, and others, make excellent processors,
but Intel is by far the leading manufacturer of PC microprocessors. Intel has consistently set the standard by which all processors are measured.
Intel 8086 and 8088
In 1978, Intel introduced the 8086 microprocessor, which had a clock speed of 4.77MHz (megahertz). The clock speed of a processor is the speed at which the CPU operates. Clock speeds are rated in megahertz or millions of electronic cycles per second. A computer rated at 5MHz has five million processing cycles per second.
The more cycles per second a computer supports, the more instructions it can execute. Remember that most instructions, because they include many processing steps, including memory transfers, ALU operations, etc., require more than a single CPU cycle to complete. The 8086 was capable of running about 0.33 MIPS (million of instructions per second). MIPS is a standard used to measure the processing power of a processor. The 8086 processor, which included 29,000 transistors, was a 16 bit processor (its data bus was 16 its wide) and had an address bus of 20 bits. It could address 1MB (megabyte) of memory, which was an incredible amount at the time. The 8086 was not a popular choice for PCs, but it did create a baseline for all future Intel 80x86 processors.
A year later, Intel reduced the data bus of the 8086 to eight bits and released the 8088 that still had a 20 bit address bus. In all other respects, the 8088 was a clone of the 8086, including the number of transistors and its clock speed. IBM chose to use the 8088 for its first personal computer, the IBM PC XT.
As shown in Figure 3 11, the 8088 (and 8086) were packaged in a 40 pin dual inline package (DIP) integrated circuit. Figure 3 11 also shows how each of the pins was designated to a particular value or function. This is common on microprocessors and integrated circuits.
A second version of the 8088 was released later that added the Turbo feature and allowed the processor to run at two clock rates, the regular 4.77MHz and a new Turbo at 8MHz.
Intel 80286
Computer manufacturers largely skipped over the next Intel microprocessor generation, the 80186, to adopt the Intel 80286 (see Figure 3 12). IBM chose the 80286 for its next PC release, the PC AT. The 286 processor, as it was commonly known, was released in early 1982 with a 6MHz clock speed, 134,000 transistors, and nearly three times the power of the 8086 with 0.9 MIPS. The 286 was able to address 16MB of memory with its address bus expanded to 24 bits. Its data bus was also backward compatible to the 8086's original 16 bits. Later 286 versions had clock speeds of 1OMHz and 12MHz.
Intel 80386, 80386DX, and 80386SX
Intel released the 16MHz 80386, commonly called the 386, in 1985. The 386 microprocessor was a full 32 bit processor packaged in a 132 pin PGA package. The 386 had 275,000 transistors and had the clock speed to support over 5 MIPS.
While it had a 32 bit mode, which meant it was able to move data in bytes, 16 bit words, or 32 bit double words (or dwords). Two features provided by the 386 were improved virtual memory capabilities that allowed large amounts of memory to be temporarily stored on the hard disk and instruction pipelining, a process that preloads and pre evaluates complex instructions, which results in faster processing speeds. The Intel 386 had versions with dock speeds ranging from 16MHz to 33MHz. However, other manufacturers, specifically AMD and Cyrix, had competing processor versions with speeds up to 40MHz.
The 386DX
The first of the 386 processors introduced by Intel was the 386DX. The 386 was a true 32 bit processor and included 32 bit internal registers, a 32 bit internal data bus, and a 32 bit external data bus. It was built with a new technology called VLSI (Very Large Scale Integration) with 275,000 transistors. The 386 used less power than its predecessors, including the 8086, because it was constructed of CMOS (Complementary Metal Oxide Semiconductor) materials, a way of manufacturing transistors that reduces the amount of power required when idle.
The 386DX could address up to 4 gigabits of system memory, but its built in virtual memory management (VMM) system allowed VMM enabled software access a virtual memory store of the equivalent of 64 terabytes (TB) of memory (a terabyte is a trillion bytes of memory).
The 386SX
Intel also released a lower cost version of the 386 processor called the 386SX. The primary difference between the 386SX and the 386DX was that the SX model had only a 16 bit external data bus and a 24 bit address bus, which made it backward compatible to the 286 processor. The 386SX was released to fill a market need, which was a lower priced processor with the power of the 386DX at the cost of the 286.
The 386SL
Intel released the 386SL, which was a 20MHz processor, in 1990. The SL version was similar to the 386SX, but it was specifically designed for portable computers, featuring improved power management functions.
Intel 80486DX and SX
Processors did not break the one million transistor barrier until Intel released the 25MHz 486DX microprocessor in early 1989. This processor had over 1.2 million transistors and generated 20 MIPS. This processor also introduced a number of innovations, including the inclusion of processor cache (Level I cache) on the processor chip, the introduction of burst mode memory access, and for the first time, an integrated math coprocessor. Before the 486DX, if a user wished to speed up the math functions on a PC, a separate math coprocessor had to be installed. The 486 was packaged in a 168 pin Ceramic Pin Grid Assembly (CPGA) package that required a processor mounted fan to cool it. Processors before the 486DX had relied on the system fan in the PC's power supply for cooling.
As it had done with the 386, Intel released a 486SX model in 1991 to provide a low cost processor. The primary difference between the DX and the SX models was that the SX model did not have a built in math coprocessor.
Intel 80486DX2/DX4
The next model of the 486 was released in 1992 as the 80486DX2. The "2" designation referred to a technique called overclocking that allows a processor's clock speed to be doubled. The DX2 was first released as a 5OMHz version, which doubled the DX's 25MHz bus speed, and was followed by a 66MHz version (33MHz bus times 2).
The 486DX4 was a product of overclocking as well. The 486 25MHz and 33MHz processors were overclocked to produce triple their normal clock speeds. This resulted in the DX4 processor available with 75MFIz (25MHz times 3) and 10OMHz (approximately 33MHz times 3) clock speeds.
Overclocking is the result of resetting a PC so its microprocessor runs at a higher clock speed than its manufacturer specified speed. Although this sounds like it must be illegal, it is and can be done, especially on Intel processors, because Intel is more conservative in setting the labeled speed of its processors. If you'd like more information on overclocking, visit this Web site: www5.tomshardware.com/guides/overclocking/.
AMD 5x86
Intel did not have much competition until Advanced Micro Devices (AMD) released its 75MHz 5x86 microprocessor. The AMD 5x86 processors were compatible with 486 motherboards but had similar power to the early Pentium processors.
Cyrix 5x86
The Cyrix 5x86, also known as the MlSE, was intended to compete with the Intel 486 with which it was socket compatible. Like the AMD 5x86, the Cyrix processor was able to compete with early Pentium processors.
The Pentium
Although it was known in its early development as the 80586, by 1992, Intel had discovered that model numbers could not be copyrighted. So, instead of the number, they used a trademark name, Pentium, for their next processor. This new processor, shown in Figure 3 13, included many new features, including separate 8 bit caches for data and instructions and a very fast FPU. The Pentium kept the 32 bit address bus of the 486 but added a 64 bit data bus. It also included superscalar architecture, which is a processor technology that allows more than one instruction to be executed in a single clock cycle. The clock speeds of the Pentium processor ranged from 60MHz to 20OMHz.
MMX Technology
The next version of the Pentium processor was the Pentium MMX, which had clock speeds from 166MHz to 233MHz. This version of the Pentium processor added MMX (Multimedia Extensions) technology to the Pentium along with some improved internal clock speeds. MMX technology is a set of instructions that uses matrix math (another meaning for MMX) to support graphic compression and decompression algorithms (such as JPEG, GIF, and MPEG) and 3D graphic renderings. MMX allows the FPU to act on several pieces of data simultaneously through a process called SIMI) (single instruction multiple data).
Cyrix 6x86 Processors
Cyrix, which is now VIA Cyrix, produced a family of Pentium clone processors that were designated as the 6x86 P series. The "P" value in the model name was a performance rating indicator. The 6x86 P200 indicated that the Cyrix processor with that model number had the performance equivalent of a Pentium 20OMHz processor. Cyrix produced models ranging from its 6x86 Pl2O to the 6x86 P200. The 6x86 P series had overheating problems as well as some incompatibility issues, which prompted Cyrix to produce a low power, low temperature version, the 6x86L.
Other Pentium Clones
Two other manufacturers produced processors to compete with the Pentium. The AMD K5 processor, with versions of 75MHz to 166MHz, unfortunately suffered from its own complexity, which affected its processing speeds. The Integrated Device Technology
(IDT) Centaur WinChip C6 includes MMX extensions, has a large Ll cache, and is less expensive than the 20OMHz Pentium MMX The WinChip C6, which is popular outside of the U.S., is available in 180MHz to 240MHz versions. Of the MMX clones, the WinChip C6 is the one most similar to the Intel Pentium MMX in capability and speed.
Intel Pentium Pro
Shown in Figure 3 14, the Pentium Pro, the next in the Pentium line, was developed as a network server processor. To support the demands put on a network server, the Pentium Pro has I megabit of advanced second level (L2) cache. The Pentium Pro 20OMHz version was specially designed to support 32 bit network operating systems, such as Windows NT, and to be used in configurations of one, two, or four processors.
The Pentium 11
The Pentium 11, shown in Figure 3 15, is the Intel Pentium Pro with MMX technology added. The PH, as it is commonly referred to, is available with clock speeds of 233MHz, 266MHz, and 30OMHz. It is excellent for multimedia reproduction that requires support for full motion video and 3D images.
Celeron
Developed from use in desktop and portable computers, the Celeron microprocessor, shown in Figure 3 16, is the low cost model of the Pentium 11 processor series. It features two choices for mountings, the Pentium II's Slot I and a socket style named after the number of pins in use, Socket 370, shown in Figure 3 16. The Celeron is released in versions with clock speeds of 333MHz to 50OMHz, with newer models, built on the Pentium III core, to offer clock speeds of 566MHz or faster.
Xeon
Figure 3 17 depicts the Pentium II Xeon processor, which is the successor to the Pentium Pro as a network server processor. To enhance its ability as a network server microprocessor, the Xeon features a range of L2 cache size choices, ranging from 512K, 1MB, and 2MB. The Xeon is capable of addressing and caching up to 64GB of memory with its 36 bit memory address bus. The Pll Xeon can be configured with four to eight CPUs in one server.
AMD K6
Developed to compete with the Pentium MMX, the AMD K6 outperforms it in speed and price. It is available in 166MHz, 20OMHz, 233MHz, 266MHz versions, and a 30OMHz model that mounts in a Super 7 socket.
Cyrix 6x86MX and Cyrix III
Also known as the MII, the Cyrix 6x86MX processor contains an MMX instruction set. The 6x86 MX has a performance rating (PR) of P 166 to P 366. Cyrix, which is now owned by VIA Technologies, now also offers the 6x86 in a P 433 version as well.
The Cyrix III microprocessor (see Figure 3 18) runs at clock speeds of 433, 466, 500, and 533MHz. It supports Intel's MMX and 3DNow, the AMD equivalent of multimedia extensions. The Cyrix III processor, technically the VIA Cyrix 111, is the equivalent of an Intel Pentium II Celeron processor.
AMD K6 2 and K6 III Processors
compete with the MMX technology of the Pentium processors, the AMD K6 2 processor, shown in Figure 3 19, has an added 3DNow, a set of 3D graphic instructions that extend the MMX instructions already incorporated into the K6 design. The K6 2 processors are available with clock speeds from 266MHz to 550MHz. A newer model of the AMD K6 line is the K6 2+, which has additional L2 cache on the processor chip and some new power control features.
The K6 III processor features 256K of L2 cache and clock speeds from 400MHz to 60OMHz. A newer model, the K6 111+ includes 1MB of cache and runs at the clock speeds of the K6 111.
