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The Concise Guide to PC Chips
Do you feel like you're caught in a chip blizzard? We'll help you conquer CPU confusion and decide which chip you'll want in your PC.

-- by Jonathan Blackwood and Jim Forbes

Selecting a PC used to be a breeze. You either got one with the top-of-the-line, blistering fast CPU or settled for something a little slower but speedy in its own right. It's not that easy anymore. This year we saw the most aggressive launch of new processors in microcomputing history.

MMX, Pentium II, K6, M2-who can keep up with all these chips? Intel, AMD and Cyrix all came out with brand new speed demons of 200MHz or faster this spring.

When the dust cleared, Intel faced competition in its home court for the first time in 15 years. The AMD-K6 is directly compatible with Intel's MMX instruction set, and Cyrix positions its forthcoming M2 as a cheaper alternative to Intel's new flagship processor, the Pentium II.

Given the current pace of technology, the rate of new processor introductions will probably increase. Intel and AMD will flesh out existing lines, while fringe contender Cyrix joins the battle to put its processors in the motherboard sockets of new computers.

With its 25-year history in microprocessor development, Intel remains the undisputed king of microprocessors-both in technology and market share. Market research firms note that more than $18 billion worth of microprocessors will be sold in 1997-and Intel's share of that lucrative market is 80 percent, according to Mercury Research in Scottsdale, Ariz.

Intel's Lines

Intel's Pentium is the best-selling CPU line around. Since its 1992 debut, the Pentium has set sales records and become an industry standard. Intel actively markets four processor lines: the fifth-generation Pentium P54C and P55C chips, and the sixth-generation Pentium Pro and Pentium II.

P54C processors operate at 75MHz to 200MHz. The P55C is a Pentium with MMX and runs at 133MHz to 233MHz. Intel also offers separate lines of fifth-generation Pentium CPUs for mobile computers. These include a 133MHz version of the P54C, and 150MHz, 166MHz and 200MHz versions of the P55C.

Sixth-generation processors are "superpipelined," which means they feature register renaming, branch prediction, speculative execution and out-of-order completion technologies. The Pentium Pro is available in 166MHz, 180MHz and 200MHz clock speeds. The new kid on the block, the Pentium II, includes the MMX instruction set and runs at 233MHz, 266MHz and 300MHz.

The Pentium II has 7.5 million transistors, more than double the amount of the original Pentium. It also includes the bus design for level 2 cache first used in the Pentium Pro. A new technology called Dynamic Execution speeds up performance by increasing the data that can be processed in parallel. Another key distinction between the Pentium II and the Pentium Pro is the use of a new connection scheme called a Single Edge Connector. Because of it, the Pentium II and its cache reside in a plastic and metal cartridge that plugs into a special slot called Slot One, which requires a new motherboard design.

Industry executives say Intel plans to use Slot One to protect its territory from compatible chip makers such as AMD and Cyrix. Though AMD and Cyrix's new processors may fit in some existing Pentium sockets, they are incompatible with sockets designed for Intel's patented Single Edge Connector. Don't expect Intel to license its edge connector technology to other processor makers.

The Pentium II and Pentium Pro use Dual Independent Bus Architecture, which can provide a performance boost of up to three times over older Pentium buses. A processor-to-main-memory circuit and the level 2 cache bus circuit make up the dual buses. The cache bus scales to that of the processor bus (which runs at up to 150MHz on computers equipped with 300MHz processors). The processor/main memory circuit supports concurrent parallel operations, breaking free of the sequential instruction process that caused a bottleneck in previous Pentiums.

The Other Players

AMD, founded in 1969, boasts that it has sold 85 million x86 processors since 1982 and 40 million in the last four years. That impressive figure still gives AMD only about 9 percent of the worldwide x86 market, according to Mercury Research. That may change with the introduction of its first sixth-generation processor, the K6.

AMD currently sells three basic designs: the fourth-generation 5x86, the fifth-generation K5 and the K6. The 5x86 is basically a revved-up 486 design running at 133MHz and "power rated" at PR75-meaning it offers roughly the performance of a 75MHz Pentium chip. (Because of its 486 core, the 5x86 has to run faster than an equivalent Pentium to produce the same amount of power, hence the lower PR.) This chip is sold mostly overseas and in sub-$1,000 PCs in the U.S. market.

AMD's fifth-generation K5 chip is a Pentium-class processor that's produced in two flavors: a 100MHz version, which has a power rating of PR133, and a 116.7MHz version, power rated at PR166. Neither the 5x86 nor the K5 is available in a version that's MMX-enabled.

The new K6 supports all 57 MMX instructions and is available in 166MHz, 200MHz and 233MHz versions. Expect to see 266MHz and 300MHz versions before year's end. The "PR" rating is no longer used, since the K6 is roughly comparable to Pentium Pro class or P55C processors of the same clock speed.

Cyrix, founded in 1988, got its start making math coprocessors and has no fabrication facilities of its own. Instead, the company contracts with IBM to manufacture its chips. Cyrix currently offers two sixth-generation processors: the MediaGX and the 6x86. However, the 6x86 will soon be replaced by the 6x86MX (aka M2)

The MediaGX is available in 120MHz and 133MHz versions, and provides performance roughly comparable to that of a P54C Pentium processor at the same clock speed. Though it does not support MMX, this chip includes Virtual System Architecture (VSA), which combines the functions of a memory controller, a video card and a sound card. The Compaq Presario 2100 uses this chip; it has no need for a video adapter, a sound card or separate video RAM because VSA combines these functions.

The M2 processor supports 57 MMX instructions, and will come in 133MHz (PR166), 150MHz (PR200) and 188MHz (PR233) versions. Though Cyrix processors are used primarily in inexpensive systems, their performance is relatively good. In our testing, the M2 couldn't match the Pentium II's MMX performance, but it ran applications well. The M2 will probably sell inside systems in the $1,000 to $1,500 range.

More Power, Less Cost

While the Pentium II averages a blazing 550MIPS, the Pentium Pro speeds along at an average 417MIPS, the K6 at 396MIPS, the P55C at 387MIPS and the P54C at 358MIPS. And as performance is increasing, prices are dropping.

Judging by CPU performance and total cost, new-generation desktop computers powered by chips such as the Intel 266MHz Pentium II are out and out bargains. Consider this: In 1993, top-of-the-line systems equipped with state-of-the-art processors delivered under 100MIPS and cost approximately $4,500. Some of today's new machines equipped with 266MHz processors cost under $3,800. That's $6.90 per MIPS vs. 1993's $45 per MIPS. And it looks like computing will continue to get cheaper as computer manufacturers and their semiconductor supplier partners are forced to compete on price.

The current pace of technology is as beneficial to consumers as it is to microprocessor and computer manufacturers. Desktop computers that use new processors like the Intel Pentium II and the AMD-K6 are being offered at low introductory prices-some cost less than $3,000-while pioneering new configurations. For example, most new Pentium II and K6-based machines include 64MB of system memory, high-performance video adapters with at least 4MB of video memory and hard disks with capacities starting at 4.5GB.

Systems are also more highly targeted. Because of its price, Intel's 266MHz Pentium II is more apt to be used in high-end corporate machines than in entertainment systems.

AMD and Cyrix processors are used mostly in inexpensive systems designed for the home and small business. Current low-end systems for the home often cost as little as $800 with configurations that include 133MHz Pentium MMX, 1.6GB hard disks, PCI video adapters with 2MB of video memory and 16MB of system memory.

The next level up includes processors that support Intel's MMX multimedia instruction set and run at 166MHz to 233MHz-processors such as the Intel P55C line or AMD's K6 family. Typical prices for such systems (some of which include 32MB of system memory and 3GB hard disks) range from $1,500 to $2,000, without monitors. The server market, meanwhile, is dominated by Pentium Pros, often in dual-processor configurations.

Other classes of computers are beginning to emerge or are in a state of transformation. For example, a handful of companies (primarily those in the technical and scientific categories) are moving wholesale to Windows NT 4.0 and could migrate to NT 5.0 when that begins to ship in 1998. It's not uncommon for those users to have fast processors designed to run complex custom applications that perform computationally intensive tasks. These include Intel's 266MHz Pentium, or 433MHz or 500MHz versions of Digital's Alpha processor.

New Technologies

The most significant upcoming technology is Intel's Advanced Graphics Port (AGP), which will allow 3D graphics cards to tuck texture mapping away in main system memory. Essentially a bus, AGP supports routine transfers of 200MB per second and burst transfers up to 528MBps. Intel will undoubtedly be first to market with this connector on the Pentium II motherboards, but expect AMD to follow closely behind. AMD is developing its own chipsets for its K6 processor especially for this purpose. Those chipsets would fit into Pentium motherboards modified with the special AGP connector.

Another new class of chips, known as Java processors, is being developed to take advantage of the Java programming language. NEC, Rockwell Semiconductor and Lucky Goldstar Semiconductor are among the companies expected to produce Java processors for use in so-called network computers. Those companies have licenses from Sun Microsystems, which created the Java language.

Java processors differ significantly from general-purpose microprocessors made by Intel, AMD and Cyrix. Besides being designed to directly execute Java code, they lack much of the functionality of current Pentium processors. Because network computers execute programs that reside on the Internet or corporate intranets, they don't need hard disk storage. These computers will also come with limited memory because they're designed to perform specialized rather than general tasks. Java processors are scalable, however, and Sun's technical marketing manager, Harlan McGham, says they will come in speeds ranging from 20MHz to 200MHz. Look for first-generation Java processors to appear later this year, although widespread availability won't begin until 1998.

More Speed Around the Corner

Your typical desktop PC will soon get faster. Later this year, Intel's 300MHz Pentium II will become widely available, and AMD will begin shipping its 266MHz K6, sources say. But even faster and more powerful processors are on the horizon-the near horizon.

While Intel keeps a lid on specifics about future processors, word is leaking out that 1998 will feature as many new chips as 1997. Intel will expand the Pentium II line with a 400MHz chip; it's also expected to launch a speedy and brawny new family of CPUs now being developed under the code name Merced. Like sixth-generation processors, Merced is a 64-bit chip. Industry observers predict its seventh-generation design will fuel the development of a new class of desktop and deskside machines that are more powerful than most minicomputers. Potential applications for Merced-based machines include computer-animated graphics workstations and high-performance servers.

What About Notebooks?

Processors designed for notebook computers have traditionally lagged those designed for desktops. For example, the fastest desktop chip currently shipping is a 266MHz Pentium II. The current high-end processor for notebooks is a 200MHz Pentium P55C.

But Intel is closing the gap between notebooks and desktop computers. It recently introduced a 133MHz P55C for notebooks, and in the coming months is expected to launch 233MHz and 266MHz versions of the P55C for notebooks. In 1998, sources close to Intel say the company will launch versions of its Pentium II for the notebook market.

AMD is expected to aim versions of the K6 at mobile computers. Sources close to AMD report the company is expected later this year to launch 200MHz and 233MHz versions of the K6 for mobile computers, although such designs could require special motherboards to deal with the special heat and power requirements of the sixth-generation chip.

The chip choices available today offer more alternatives for high-performance desktop PCs than ever. Only one thing is certain: There will be even more chips to choose from tomorrow.

Windows Magazine, August 1997, page 214.

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