First Tests of Athlon 64 PCs: Fastest Yet

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Advanced Micro Devices is entering the world of 64-bit computing, launching Athlon 64 CPUs that are producing some of the fastest PC WorldBench scores yet, and a handful of vendors are ready to sell you those new systems.

The new chips are the Athlon 64 FX-51, a high-end 2.2-GHz chip with dual-channel memory; and the more mainstream Athlon 64 3200+, which runs at 2 GHz and has single-channel memory.

Meanwhile, Intel is promoting its new Pentium 4 With Hyperthreading Extreme Edition. First tests find it doesn't beat AMD's entry, but the race is close.

The three Athlon 64 FX-51A-based systems first tested are a $3535 PC from Alienware; a $3245 system from Falcon Northwest; and a $3250 Voodoo unit. PC World also tested one Athlon 64 3200+ unit from ABS, priced at $1799, and a 3.2-GHz Pentium 4 comparison system from Alienware, priced at $3143. Each includes 1GB of DDR400 memory and an ATI Radeon 9800 Pro graphics card with 256MB of RAM. Pricing is without monitors or speakers.

Not tested, but in the wings, is an Athlon 64 desktop system from Hewlett-Packard. The HP T182k is also expected to ship in September.

Test Results

On average, the Athlon 64 FX-51 systems notched a PC WorldBench 4 score of 142--the fastest yet. The Athlon 64 3200+ unit from ABS scored 140, and a comparably configured Intel Pentium 4 comparison PC from Alienware managed 126. The scores for three previously tested 32-bit Athlon XP 3200+ PCs averaged 136.

All tests were performed with 32-bit software. AMD knew 64-bit desktop computing wouldn't be ready for prime time right away, so the company made sure its 64-bit Athlon hybrid processors can also run today's 32-bit software. And our initial tests show the chips run them very well.

Systems running the FX-51 show pronounced improvements in some of the more CPU-intensive tests. In particular, they were about 44 percent faster, on average, than the P4 unit in our AutoCAD test. The FX-51 PCs also stand out on Premiere tests, and post top scores on the Photoshop and VideoWave tests. The P4-based PC has the best score in our Musicmatch test.

In both games tests, the FX-51 PCs are again the clear winners, posting noticeably higher frame rates at multiple resolutions. (Lower resolutions demonstrate CPU power more than higher resolutions because the graphics subsystem contributes more at higher res.)

What Else Is New?

Besides adding 64-bit capabilities, AMD has made other improvements to its newest CPUs. They include a 1MB L2 cache (up from 512KB), a faster speed system bus based on Hypertransport technology, and new SSE 2 instructions. Probably the most important change, however, is AMD's move to an on-chip memory controller.

Traditionally, the memory controller resides on the motherboard as part of the chip set, connected to the CPU via the frontside bus. AMD's Athlon XP offers a maximum frontside bus speed of 400 MHz; Intel's latest P4s have a maximum of 800 MHz. By integrating the memory controller, AMD gives memory a private channel to the CPU so it no longer must share a pipe with other system components. Unlike on-board CPU cache, the integrated memory controller runs at the memory speed, not CPU speed.

"The on-board memory controller provides more bandwidth and drops the latency," says Kevin Krewell, general manager at analysis firm MicroDesign Resources. Lower latency means less time between when the CPU asks for data from memory and when it gets it.

The two new Athlons also have real architectural differences between them. For example, the FX-51's dual channels can move up to 6.4GB of data per second with DDR400 while the mainstream Athlon 64's single-channel DDR can move up to 3.2 GBps. More: The FX-51 requires a 940-pin socket (the Athlon 64 3200+ uses the new Socket 754) and more expensive registered-memory DIMMs. Usually reserved for servers, a registered DIMM includes an internal buffer that allows more memory chips per DIMM, but with a delay of half a clock cycle required to help prevent spontaneous errors. The FX-51 is also easier to overclock than the Athlon 64, although AMD won't officially recommend doing that (it still voids the warranty).

At launch, AMD is charging PC vendors $733 for each FX chip in quantities of 1000, compared with $417 for the Athlon 64 3200+ (Intel's 3.2-GHz P4 is selling for $637). That's a hearty premium for the FX-51 product, but it's a price that performance buffs are likely to pay, says Dean McCarron, principal analyst with Mercury Research.

There should be little confusion between AMD's two new chips, but you'll note the company gave the 2-GHz Athlon 64 the same 3200+ performance rating as that of its last 32-bit Athlon XP chip (64-bit FX-designated chips dropped the performance-rating scheme altogether). Check carefully before you buy: AMD will continue to sell both 3200+ CPUs for the near future.

What's With 64 Bits?

The arrival of 64-bit desktop computing is at hand: AMD's launch of its Athlon 64 chips--along with Apple's release of its G5 desktops--means 64-bit processors, once reserved for servers and high-end workstations, are now in systems available on retail shelves.

In time, 64-bit systems could change the face of desktop computing. That's because a 64-bit processor can run longer, more complex instructions than a 32-bit chip, improving the performance of data-intensive tasks such as audio and video encoding, advanced engineering design apps, and, naturally, games.

Equally important is a 64-bit CPU's capability to recognize and use much more memory. Today's 32-bit chips, including Intel's Pentium 4 and AMD's Athlon XP, can address a maximum of 4GB of memory split between the OS and applications. Few desktops have that much memory, and even fewer apps use it. But in time and with ever more complex software, that limitation may become a bottleneck, making a 64-bit processor's theoretical capability to address a whopping 16 billion gigabytes of memory quite attractive.

But you will need a 64-bit-capable operating system, new hardware drivers, and 64-bit applications to fully take advantage of such a processor, and therein lies the rub.

Several Linux distributions, notably Red Hat, now support the Athlon 64, but Microsoft's Windows XP 64-Bit Edition for 64-bit Athlons won't arrive until next year. Aside from a handful of expected applications, such as DivXNetworks' DivX video encoder, 64-bit desktop software will be an even longer wait. The lack of full software support is one reason Intel does not currently plan to introduce a 64-bit desktop chip.

Apple's latest OS X has 64-bit extensions, providing the new G5 systems and a handful of optimized apps a taste of greater power. But that isn't quite enough to give Apple a wholesale performance edge.

Market Views Differ

So if the Athlon 64 and Athlon 64 FX perform so well for 32-bit computing, why is AMD pushing the 64-bit angle at all? Because company executives believe the 64-bit desktop age is dawning now.

Once video editors watch a 64-bit PC encode video directly to a DVD on the fly, they'll want one, says Rich Heye, vice president of AMD's microprocessor unit. And once gamers see the cinematic quality that 64-bit chips help make possible, they'll want one.

Though mass-market adoption will take a few years, "the average lifetime of a PC is three to four years, and I think a lot of people will be running 64 bits before that's up," Heye says.

Executives at Intel disagree, seeing 64-bit computing as largely a server and workstation technology for the short term.

"With just 5 percent of servers using 64-bit addressability, there is little need [for 64 bits] today on the desktop," says George Alfs, Intel spokesperson, adding that the capability means little without accompanying software and other tools to make it work at its best.

History shows transitions like this do take time. Ironically, back in 1985 when Intel launched its 386 processor--a 32-bit chip that also ran 16-bit code--AMD claimed the extra bits weren't yet necessary. And Windows didn't become a pure 32-bit OS until Microsoft launched XP in 2001.

What's Next?

MDR's Krewell sees Intel's resistance to 64-bit computing on the desktop as a move to protect its sizable investment in its 64-bit Itanium CPU, designed for servers and workstations.

Krewell says he's convinced Intel has a backup plan should AMD's 64-bit computing initiative take off. "There is no technical reason they cannot implement a 64-bit extension in their desktop chips," he says.

Intel's Alfs says the company will continue to focus on "bringing benefits that PC users can use now." To that end, the company is promoting the 3.2-GHz P4 HT Extreme Edition, aimed at gamers who want top performance. This 32-bit chip boasts 2MB of L3 cache to speed users through their games.

Intel's next-generation chip, code-named Prescott, will also debut before year's end. Prescott's improvements include a larger L2 cache, new instructions, and improved hyperthreading technology.

In the meantime, with the Athlon 64, AMD has clearly reignited the so-called chip wars. For users, that's always good news, says MDR's Krewell.

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