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BACK in the prehistoric days of personal computing—say, ten or 11 years ago—your computer buying choices were simple. You could buy an Apple II or an IBM-PC. But then some ex-Texas Instruments employees formed a company called Compaq Computer Corp. and designed a computer that used the same microprocessor as the IBM-PC and ran the same software. After Compaq proved that IBM-PCs could be "cloned," everybody got into the act, and suddenly things got very complicated. Things have never been more complicated than today when there are at least four major types of microprocessors, all made by Intel Corp., from which you can choose: Pentium, Pentium Pro, Pentium with MMX Technology, and Pentium II. And that doesn't begin to count microprocessors manufactured by lesser-known companies such as Cyrix and Advanced Micro Devices (AMD). And let's not forget the PowerPC chip at the heart of computers made by Apple Computer Inc. and others. Why is a microprocessor so important? Because it is the brains of your computer. It's the microprocessor that uses your PC's software to turn information on your hard drive (or input from your keyboard) into useful documents such as business reports, term papers, newsletters, and mailing labels. More technically, a microprocessor is a wafer-sized piece of semiconductive silicon etched with microscopic pathways resembling a Southern California interchange. The etched pathways conduct electricity more readily than the non-etched part of the wafer and connect tiny electronic switches called transistors. A program built into the chip (known as microcode) uses information from the computer's software (also called programs or applications) to direct bursts of electricity around the pathways and, in the process, make calculations that eventually determine the results displayed on your computer monitor. The microprocessor is also called the central processing unit (CPU), although this term is occasionally used to describe the cabinet that holds the microprocessor, hard drive, power supply, and other electronics. The microprocessor is also generically called a chip. Ever since IBM designed the first IBM PC, Intel has made the overwhelming majority of CPUs that run IBM-compatible PCs. As a consequence, it is Intel and not IBM that has determined the technology of personal computers through successive generations of CPUs. From the 8086 and 8088 to the 80286, 80386, 80486, and Pentium series, it is Intel and its CPUs that have dictated the direction of computing. (NOTE: The higher the number of the chip, the newer and faster it is. The Pentium series of chips are the latest microprocessors; the latest is the Pentium II, which was released in May 1997.) Usually, Intel has moved PC development forward in a straight and orderly fashion. Each new generation of microchip offered a distinctive advantage in speed and capabilities over its predecessors. There were exceptions, such as the 80386SX or "crippled 386" chip, but PC buyers could almost always determine that the newest chip was the best chip available. That changed with the Pentium, when Intel introduced four different "flavors" of the chip. These four chips share the same basic technology, but each was developed with specific users in mind. Simply because the MMX and Pentium II chips are the newest, that doesn't necessarily mean they are the best chips for you. Nor does the fact that the "plain vanilla" Pentium chip is the oldest of the three mean that it's not the best of the three options for the way you use a computer. Which Pentium chip is best for you? In a nutshell, here is what you want to consider.Pentium with MMX technology. If you want to regularly run multimedia applications such as games, multimedia encyclopedias, or full-motion video downloaded from the World Wide Web, consider a computer with an MMX CPU. The Pentium with MMX is also the preferred chip for running three-dimensional (3-D) drawing, photo-editing, and other graphic-intensive programs. Pentium II. You probably will see fewer computers with this chip in the PC section of a computer store than PCs with the MMX chip. The Pentium II incorporates MMX technology into a chip designed for business applications in desktops, workstations, and servers. Pentium Pro.
This CPU is best if you want to regularly use extremely complex
databases, spreadsheets, and other numerically intensive applications.
Of the four Pentium-class chips, the Pentium Pro and the Pentium
II are the best choice for a network server, particularly for
networks that perform transaction processing tasks, such as recording
sales or recalling customer records. (A network server is a computer
that controls access and offers resources to other computers
that are interconnected.) If you can fit yourself into one of these categories, read no further. You have your answer. But as they say in car commercials, your mileage may vary. Even though you routinely use your PC for simple word processing, for example, you may occasionally use it for teleconferencing (viewing, talking with, and sharing programs with other computer users via a modem and phone lines). If that's the case, you should invest in a Pentium MMX machine because of its multimedia capabilities. That is just one exception among many. So you can make an even more well-informed decision about which microprocessor best fits your computing needs (and hold your own while discussing PCs with all the computer geeks at the water cooler), here's a description of the microprocessors and how they differ from one another. The Vanilla Pentium.The first Pentium chip made by Intel and the Pentium-class clone chips made by Intel's competitors are the most basic CPUs available on new IBM-compatible PCs. Nevertheless, these "plain vanilla" Pentiums and clones have all the power needed to run 90% or more of the software available. Only a few exceptionally intensive multimedia programs and high-end business programs require more power than an ordinary Pentium chip can deliver. The Pentium was a dramatic step forward from its predecessor, the 486-class microprocessor, when it was introduced in March 1993. The first 60 megahertz (MHz) and 66MHz Pentiums executed instructions 50% faster than the 100MHz 486DX4, the fastest of Intel's 486-class chips. (A megahertz equals 1,000 cycles per second.) How were the first Pentiums able to run faster than the 486DX4 even though they had a slower clock speed? To begin with, the Pentium packed 3.1 million transistors into the Pentium, nearly twice the 1.6 million transistors of the 486DX4. That's roughly equivalent of replacing a four-cylinder automobile engine with an eight-cylinder engine. (Clock speed is the rate at which the system clock paces, synchronizes, and coordinates the operations of the computer's circuits.) More important was what Intel did with those extra transistors. The Pentium incorporated a new technology called dual pipelining. When a program sends a long, detailed command to the Pentium, it can break down the command into two shorter commands and execute them simultaneously. To use a mathematical analogy, say you are given the equation (4 times 26) plus (256 divided by 8) equals X. The older 486 chips execute the first part of the command (4 times 26), store the result, then execute the second part (256 divided by 8), and then add the previous result (104) to the second result (34) to calculate X (138). With dual pipelining, one "pipeline" of the Pentium executes one command (4 times 26) at the same time another pipeline executes the other command (256 divided by 8). Dual pipelining enables Pentiums to execute more software commands (called "instructions" in computer jargon) per cycle than the 486. Another notable feature incorporated into the Pentium was the addition of on-chip circuitry hardware to calculate commands involving floating points, a type of mathematical element used in some software programs. Intel has made continuous improvements to the Pentium chip. Reducing the size of the circuitry from 0.8 microns to 0.35 microns enables today's Pentiums to run cooler and require less electricity than the original versions. And the fastest Pentiums today operate at 200MHz and execute instructions at a rate more than 300% faster than the 486DX4. (A micron is one-millionth of a meter or one-thousandth of a millimeter.) The Pentium turns Pro.Although the Pentium Pro carries the Pentium name, and incorporates many of the advances made by the Pentium, it is really a next-generation chip. This means it is based upon a new technology. In fact, development on the Pentium Pro began two years after development began on the Pentium. The code names for the two projects—P-6 for the Pentium and P-7 for the Pentium Pro—reflected entirely different generations in microchip development. The Pentium Pro, introduced in November 1995, has 5.5 million transistors, about 75% more than the Pentium. The Pentium Pro also can input and process 64 bits of data at a time while the Pentium can input 64 bits of data at a time, but process only 32 bits at a time. The Pentium Pro has taken the Pentium's design further by incorporating five pipelines: one for storing data waiting to be processed, two for executing routine instructions (integer calculations), one for making floating-point operations, and one for storing the results of processed data. The Pentium Pro makes maximum use of these pipelines through a process called "out of order" execution. That is, when it splits up a complex set of instructions into simpler instructions, it doesn't necessarily send them through the pipeline in their original order. It sends them through the pipelines in the order that will get the job done fastest. Using another mathematical analogy, take the equation [(256 divided by 8) plus (22 divided by 2) plus (2 times 3)] equals X. Although (2 times 3) is the third part of the equation, the Pentium Pro might send it through the first integer pipeline first because multiplication problems take less time to solve than division problems. Then it might load the first part of the equation (256 divided by 8) into the second integer pipeline. By the time the first part of the equation is loaded into the second integer pipeline, the third part of the equation (2 times 3) has been calculated and the second part of the equation (22 divided by 2) can be loaded into the now-empty first integer pipeline. This is only a rough analogy, but it offers an idea of the principles involved. It also shows how Intel used some creative programming to get even better performance from some already spectacular engineering. A far simpler piece of engineering has an equally dramatic affect on the performance of the Pentium Pro: a 256-kilobyte (KB) Level 2 (L2) cache piggybacked onto the microprocessor. A cache stores program instructions and data that have been used by the processor in temporary memory so it can be quickly recalled. For example, if you tell your computer to change the font in a document, the cache stores this instruction in the cache. Then if you decide to change the font again, the processor doesn't have to go to the hard drive to retrieve the "change font" instruction, dramatically improving the speed of the computer's operation. Before the Pentium Pro, part of your computer's random-access memory (RAM) could be used as an L2 cache. But that meant the processor had to wait while the cached instructions were sent from the RAM chips (also known as single in-line memory modules [SIMMs]) over the motherboard (the computer's main circuitboard) to the processor. Piggybacking the cache into the processor eliminates the delay. The L2 cache comes in particularly handy on network servers. By caching information, the L2 cache eliminates bottlenecks caused when two or more client computers try to access the network server at the same time. (Like the original Pentium, the Pentium Pro also has an 8-kilobyte Level 1 [L1] internal cache built into the processor itself. The L1 cache stores the most recently used instructions.) The Pentium Pro can use hard drives containing up to 64 gigabytes (GB) of data compared to an ordinary Pentium or Pentium with MMX, which can use hard drives containing a maximum of 4GB. That doesn't mean much for the ordinary computer, which is unlikely to access a hard drive containing more than 2GB of data. But it can mean a lot for a network computer connected to a RAID (redundant array of inexpensive discs) drive containing up to 64 gigabytes of data. The 64GB of addressable memory (along with the L2 cache) makes the Pentium Pro a good processor for network servers. MMX: the multimedia chipIntel refers to this CPU incarnation of the Pentium as the "Pentium with MMX Technology," but we unwashed masses usually refer to the chip simply as the "Pentium MMX" or the "MMX chip." Whatever the name, it is a souped-up version of the original vanilla Pentium chip. Think of it as vanilla with chocolate sauce, whipped cream, and a cherry on top. The Pentium MMX sports 4.5 million transistors, about 50% more than the original Pentium. Those extra transistors are used to execute 57 new instructions built into the chip and a 16KB Level 1 internal cache. These new instructions make the MMX CPU a hot property for running multimedia programs such as full-motion video, games, and 3-D drawing and animation programs. The new instructions built into the MMX chip enable software programs to perform a complex task—such as rotating a 3-D object—that used to require two or more instructions. This reduced number of instructions means the chip executes tasks more quickly. To really enjoy the benefits of MMX technology, you will need to invest in software written to take advantage of the new MMX instructions. The MMX instructions have absolutely no impact upon non-multimedia tasks such as word processing or recalculating a spreadsheet, but even these staid, businesslike applications get a performance boost from the MMX CPU as evidence by the growing users for the Pentium II. The MMX chip's 16KB internal cache is twice the size of the original Pentium's 8KB cache, which means the MMX can store more instructions and retrieve them more quickly than the original Pentium. A new microcode called single instruction-multiple data (SIMD) also boosts MMX performance. Instead of performing the same repetitious instruction four or five times with different bits of data, the instruction can be applied to all six bits of data simultaneously. Between the 16KB internal cache, SIMD and other innovations, reviewers agree the Pentium MMX delivers about 10% better performance than the original Pentium for non-MMX uses. Multimedia for businessIntel extended MMX technology to the workplace with its Pentium II chip, introduced just four months after the MMX chip. The Pentium II chip has been accurately described as a Pentium Pro chip with MMX capabilities. Like the Pentium Pro, the Pentium II is intended for use on high-end desktops, workstations, and servers to extend the multimedia capabilities of PCs used for business applications. Models are available for 233MHz, 266MHz, and 300MHz PCs, and the chip offers the highest performance on PCs running Win95, Windows NT, or Unix. The Pentium II, like the Pentium Pro, also features 64-bit Dual Independent Bus (DIS) architecture, which is comprised of 8-byte L2 cache bus and the 8-byte system bus. The Pentium II can use both buses simultaneously to boost the bandwidth of the CPU's output, leading to faster performance on high-end machines. Purchase planningNow that you know the details (well, enough of them, anyway), you have a decision to make: Should you buy an ordinary Pentium, or spend the extra money for a Pentium Pro, Pentium MMX, or Pentium II? The price differential between the first Pentium and the newer models is narrowing to the point that it should play little role in your buying decision. Instead, base your choice upon how you use your PC. Like the rest of the marketplace, the microprocessor industry is becoming more focused on the consumer. This is a dramatic departure from tradition, which dictated that Intel design processors with new features that nobody knew how to use. By the time software designers and the public learned to use those features, Intel had introduced a new chip. Intel dictated the technology and the rest of the world acceded to its will. Intel can no longer display such intentional or accidental hubris. Rather than attack Intel head-on, other computer industry giants are developing niche products that don't require Intel processors. For example, so-called "dumb" terminals lack their own processor but deliver all the features most PC users need. Intel has seen the writing on the wall, and the writing says "specialize." Already, Intel is designing a chip code-named "Deschutes" with symmetric multiprocessing capabilities—that is, two or more Deschutes chips will work in concert in a computer, divvying up processing tasks for advanced scientific and networking applications. When it comes to buying a computer, the menu is getting longer all the time. But if you choose based upon your wants and needs (and not price alone), you can make your computing experience enjoyable for a good, long time. |
| April Miller Cripliver, a regular contributor and creator of our popular Boot Camp column, is Director of PC Applications at the Computer Education Institute in Chesterton, Indiana. Contact April at userfriendly@bigfoot.com. |
