Speed, Speed and More Speed -- A procession of new processors-with Intel's Pentium III and AMD's K6-3 leading the way-are here. What's new about these chips-and what can they do for you?
Jonathan Blackwood, Senior Technology Editor
It's hard to tell what's moving faster these days-your business or the computing industry that keeps churning out new products. With Intel Corp. marching out its new Pentium III processors, and Advanced Micro Devices (AMD), Cyrix Corp., Integrated Device Technology (IDT) and others responding with new chips of their own, it can be confusing to determine which CPUs should power your PCs.
To make the best choice, you need to know what these new chips can do and what developments are looming in the not-too-distant future.
New Generations of Chips
Intel has been busy this year. Its new Pentium III processors, with speeds up to 500MHz and the new SSE-Streaming SIMD (Single Instruction, Multiple Data) Extensions-instruction set, have gained the most attention. (See News, this issue.) But Intel also rolled out souped-up versions of its low-cost Celeron chips, with speeds that rev to 466MHz. Mobile Celeron processors debuted at speeds up to 333MHz. (These Celerons are among the newer Mendocino chips, using the same processing core as the PII, with 128KB of on-chip level 2 cache.) Intel also introduced another mobile processor-the 366MHz Dixon chip-which uses a PII core with 256KB of on-chip level 2 cache.
AMD's new offerings feature its K6-3 processor, which has AMD's 3DNow instruction set, plus 256KB of on-chip level 2 cache. Current speeds top out at 450MHz, which yields blistering performance on business apps thanks to its motherboard-based level 3 cache (additional cache that runs at the system bus speed). In fact, the first 450MHz K6-3-powered production PC we tested achieved the fastest performance we've seen to date on our Word macro benchmark test. AMD is also shipping new mobile K6-2 processors with 3DNow, at speeds up to 380MHz. (See News, this issue.) That gives AMD a momentary advantage in mobile clock rates, but Pentium II-based notebooks are still somewhat faster because the K6-2 lacks on-chip level 2 cache.
You've probably noticed a trend with these new chips: moving the level 2 cache onto the chip die. This boosts performance dramatically because the level 2 cache can run at the full speed of the processor. Intel was the first to do this with its Mendocino Celerons. It's possible to do this now because the current 0.25-micron manufacturing process allows packing the required number of transistors into a chip of a practical size. For example, without on-die level 2 cache, AMD's K6-2 has 9.3 million transistors on an 81mm2 die; the K6-3, with its level 2 cache on the die, has 21 million transistors on a 135mm2 die.
The more transistors you can cram onto a piece of silicon, the more features a chip can offer. The next process size, 0.18 micron, will make it likely that video and so-called north bridge functions-PCI bus, DRAM bus, AGP bus-will be included on highly integrated chips that should appear later this year and early next year. And, of course, you can count on higher clock speeds.
With these new processors, business users are likely to benefit mostly from the higher processing speeds; the multimedia niceties have yet to be fully exploited. When applications using the advanced graphics functions do appear, these chips will be a boon for users who work with complex graphics.
Inside the Pentium III
What's new in the Pentium III? The most important issue at present is speed-500MHz now, with 600MHz expected this summer. Then there's SSE, 70 new instructions intended to accelerate 3D graphics and streaming data types such as video and audio. Despite all the hype about the SSE instructions, there are few business applications that make use of them yet, except for specialized apps such as Dragon NaturallySpeaking or Adobe Photoshop.
If more software developers opt to harness SSE, the new instructions could improve the quality of videoconferencing, speech recognition and other media-rich apps. But if software vendors' relative lack of interest in the MMX instruction set-SSE's predecessor-is any indicator, don't expect this to happen soon. Intel also claims SSE will improve Internet performance, but bandwidth, not processor power, remains the biggest bottleneck there.
Since Intel didn't really improve the P6 core itself with the Pentium III, don't expect any improvement over a Pentium II-other than that afforded by clock speed-on non-SSE-enabled apps. But higher clock speed alone might not be enough to distinguish the Pentium III. For typical business applications-word processing, spreadsheets and Web surfing-300MHz is wholly sufficient. A 500MHz PC might be overkill, especially considering its cost: A 500MHz Pentium III will cost at least $2,200, while a 333MHz-class PC can be had for well under $1,000.
The Pentium III's SSE instructions will be a market differentiator, becoming the key distinction between Intel's low-cost Celerons and its higher-priced offerings as the Celeron achieves higher and higher clock rates. The distinctions among Intel processors grow even murkier when you consider that hardware hackers routinely overclock their Celeron systems all the way to 500MHz (don't try this yourself!). And while Intel has demonstrated a Pentium III running at 1 gigahertz, the company has also designed the chip so that it can't be overclocked. Expect such circuitry to be built into future versions of the Celeron.
But perhaps the most important new product from Intel will be its Camino (440JX) chipset-which should be out by the time you read this. The 440JX chipset will ramp up the bus speed to 133MHz and enable the use of Direct Rambus Dynamic RAM. Direct RDRAM offers impressive speed, with a peak bandwidth of 1.6GB per second compared with SDRAM's 125MBps.
AMD Still on Intel's Heels
AMD scored a coup in March when it was reported that its retail-outlet sales had topped those of Intel-based PCs. This was widely misinterpreted to mean that AMD had outsold Intel, period. In fact, AMD remains a distant second to Intel. Still, most major PC vendors-with the notable exception of Dell Computer Corp.-now offer at least one PC line featuring AMD processors.
AMD's processors offer excellent performance, unquestioned compatibility and great value. AMD's K6-2 and K6-3 processors both include the 3DNow instruction set for improved 3D graphics performance. By putting the level 2 cache on the K6-3, where it runs at the same speed as the chip, AMD has improved performance. It has also eliminated the principal downside of its Super7 motherboard architecture-the lower clock speed of its level 2 cache-when compared to Intel's Slot One design.
When its K7 appears later this year (it's expected in the fourth quarter), AMD will compete head-to-head with Intel's Xeon processor for the workstation and server markets. The K7 offers a host of improvements, including three floating-point units (FPUs), 128KB of level 1 cache and a new Slot A connector, with electronics and chipset borrowed from Compaq's Alpha processor. It promises to be a screamer, processing three instructions per clock cycle (previous x86 CPUs maxed out at two), and can be used in multiple-processor configurations.
Cyrix in the Wings
Cyrix's M II processor is used in many entry-level PCs, but the company has been slow to introduce its new Jedi chips. The Jedi chips use the new Cayenne core, adding dual MMX units (to match Intel), a fully pipelined FPU and 3DNow instructions. Cyrix's upcoming MXi processor will integrate graphics functions with a Cayenne core. Chips with the new Jalapeno core won't arrive until 2000. The Jalapeno design offers 256KB of on-chip level 2 cache, along with deeper pipelining for higher clock rates and lower latencies for complex functions.
Cyrix will continue to target the entry-level market with highly integrated MediaGX chips that have on-chip graphics and memory controllers. Its new "PC-on-a-Chip" processors, intended for peripherals such as DVD players and information appliances, carry integration a step further by combining MediaGX-type functions with TV tuners, DVD decoders and audio processing units.
Rounding Out the Field
IDT's super-inexpensive WinChip is used mainly in so-called "white box" PCs built by very small suppliers. IDT has been slow to introduce its WinChip 2+ processors, but is working on integrating north bridge functions onto the chip die, along with a larger, 128KB level 2 cache. Moving forward, IDT intends to offer a new core design allowing 600MHz or higher clock speeds.
Rise Technology will offer a simple, low-power design aimed at value-class notebooks. Another company, Transmeta, has been secretive about a RISC-like chip that processes x86 code in an emulation mode that's expected in the fourth quarter of this year.
What to Buy
While the lure of the newest, fastest chips is overpowering, the truth is your business is likely to hum along quite well if your workers are toiling away at PCs powered by 300MHz-or-so Pentium II, K6-2, Celeron or even M II processors. Systems built around these chips are moderately priced and perform well with typical business apps. If, on the other hand, your business relies on more specialized applications that crunch their way through multimedia data, you'll want the kind of power the new Pentium III or K6-3 machines offer. And, as usual, you'll have to pay a premium for that power, although K6-3-based systems should cost several hundred dollars less than Pentium III systems.
Whether a PC powered by one of these hot, new processors is in your immediate future or not, you can be sure of one thing: Even faster chips are just around the corner.
SIDEBAR: Thin Is In
Speedier chips are largely the result of advances in the manufacturing process that reduce "wafer thickness." But this concept is often misunderstood. The difference between a 0.25-micron and 0.18-micron wafer is not the thickness of the chip, but the width of the tracings on the wafer and the distance between them. It's as though you photocopied a drawing of the microprocessor circuitry and reduced it to 72% of its original size.
There are two ways a manufacturer can take advantage of reduced tracing widths. First, the smaller size of the circuitry on the same-size wafer (a disc of silicon usually 5 or 8 inches in diameter), means that more copies of each processor can fit on a given wafer. Given the economies of scale, the manufacturer can then make more money, or reduce the price of the processor.
Another way to take advantage of this technology-as Intel and AMD are doing-is to keep the number of processors per disk constant, and use the additional space to pack in more features, like on-chip level 2 cache now, and on-board video or north bridge functions later.
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