Money for Nothing? Rambus Performance Falls Short

SAN FRANCISCO (06/23/2000) - For months, we've wondered when Rambus Inc. dynamic RAM would begin to demonstrate real-world performance benefits that match its high cost. We're still wondering. Head-to-head against today's standard SDRAM PC memory, it's a tie, at best.

PCs shipping with RDRAM since last fall have quelled some complaints about the pricey new memory by delivering a number of good benchmark results. But it has been hard to tell if other factors, like souped-up 3D graphics boards or faster processors, were responsible for improved performance. To clear the air, we isolated the effects of RDRAM by testing identically configured 800-MHz PCs that use either RDRAM or SDRAM technologies.

The upshot: RDRAM delivers only a slight performance advantage to some graphics-intensive software but offers virtually none to office applications.

RDRAM could come into its own when faster, more demanding CPUs from Intel arrive, and if multitasking of data-intensive software becomes more common. But it must contend with the new Double Data Rate DRAM memory technology.

Things Being Equal

The PC world Test Center custom-built two of the test PCs using Micro Express cases and Intel and Asus motherboards. We also tested two PCs from Dell and four custom units from Micron Technology. All PCs were tested with our PC WorldBench 2000 suite of office applications, graphics programs, and more.

A Dell Dimension PC using RDRAM on a 700-MHz bus between CPU and memory (called PC700) scored 151 on PC WorldBench 2000, just a point higher than a fellow Dell with 100-MHz (PC100) SDRAM. The four Microns, representing RDRAM, DDR SDRAM, PC100 SDRAM, and the new 133-MHz (PC133) SDRAM, also showed negligible differences on this test.

On our Quake III test and's 3DMark2000 tests, DDR and PC133 SDRAM PCs performed a shade faster in most runs than RDRAM units. But RDRAM consistently nosed out a win on the AutoCAD test. Usually trailing, but not by more than 10 percent, were systems with PC100 SDRAM, probably because they have the slowest memory bus. Save for these PCs, most users would be hard-pressed to notice any differences.

Pros And Cons

Rambus's biggest strength is its high throughput, which lets it pump three times more data per second than PC100 SDRAM. Its alleged weakness is latency, the delay between the time data is requested from memory and when it's delivered to the CPU. Current CPUs, software, and tests tend to exacerbate Rambus's shortcomings and work against its strengths, say memory experts.

Longer latency hampers performance in programs like word processors and certain databases, which tend to jump around a lot making small data requests from memory. It's less of a problem when you're watching DVD movies or editing video, where megabytes of data get blasted out, then stop for a while. RDRAM's greater throughput also comes into play with these types of applications. But as Nathan Brookwood, principal analyst at Insight 64, put it, "The benefit [of Rambus] compared with the pricing is out of line."

Rdram typically adds $150 to $350 to the cost of a preconfigured PC--not an absurd premium, but disproportionate to its slight speed increase. It's on upgrade chips where price differences are stunning. One May posting at Kingston Technology's site listed 128MB of the slowest, cheapest RDRAM for $370 more than the fastest non-DDR SDRAM, and 256MB RDRAM modules for $750 more than 256MB of PC133 SDRAM.

Prices should drop as vendors learn to make RDRAM more cheaply. "A year from now, I think a price premium for Rambus in the range of 25 percent compared to SDRAM is very achievable," says Avo Kanadjian, Rambus vice president of worldwide marketing.

What's so great about a premium of only 25 percent?

Enter DDR

Intel archrival AMD favors DDR over RDRAM. Its price premium is better--8 to 10 percent for now, expected to drop to 5 percent when volume production begins, says Semico Research vice president Sherry Garber. And DDR should have less of a latency problem than RDRAM.

But while DDR's maximum throughput is twice that of current SDRAM and competitive with RDRAM, it won't approach that of a forthcoming dual-channel RDRAM. Motherboard design issues related to DDR's wide data bus caused some concern, too.

Bob Eminian, vice president of marketing at Samsung Semiconductor, a manufacturer of all four memory types and the highest-volume RDRAM vendor, dismisses these concerns, saying designers have been working out technical issues for more than two years. "We're forecasting that by the end of next year, Rambus and DDR will hold about the same market share," Eminian says. (The forecast doesn't include DDR SDRAM in graphics boards.) Expect to see AMD Athlon PCs with DDR later this year; the memory is already appearing in high-end servers.

No Case For Now

kanadjian says people will want RDRAM for playback of downloaded graphics files

that will finally show Rambus in its best light. Eminian agrees. He also says

RDRAM will show its value when businesses use Windows 2000's improved multitasking to do background data backups, network distribution of large files, and such.

Rambus will also get a boost from Intel's next generation CPU, code-named Willamette. Expected in the second half of this year, the new CPU will require the dual-channel Rambus. When Willamette eventually migrates down to midrange and even low-end PCs, RDRAM will enter the computing mainstream, Brookwood predicts.

RDRAM supporters cite "headroom" when asked why the average person should invest in RDRAM today. But the next-generation 1.5-GHz-and-up CPUs won't work in today's Rambus PCs, and several hundred dollars seems too much to pay for possibilities. Brian Zucker, a technology evangelist at Dell, agrees that as an investment, Rambus probably doesn't make sense for most people, and admits that Dell markets its RDRAM PCs as most appropriate for those with high-end computing requirements now.

Unless you're one of the few whose current apps show substantial gain with RDRAM, wait until the prices come down and software catches up. PC133 SDRAM should suit most of us, providing a minor speed boost on the business applications we typically use, for about the same price as today's PC100 SDRAM.

With Intel finally releasing a motherboard that supports PC133 SDRAM, this memory should soon become the mainstream standard. DDR improves performance, but its immediate future is clouded by high cost and uncertain availability.

As for Rambus, no matter how you slice it, most people just don't need it yet.

--David Essex

Athlon Thunderbird CPUs match up well against Intel PIIIs.

One Motherboard does not fit all. If you have a Rambus motherboard, you will not be able to switch to DDR, or vice versa.

One of the first DDR PCs, built for us by Micron Technology.

Intel's Latest Chip Set Chronicles

Filling a gap in its motherboard lineup, Intel has just released three new chip sets. The 815 and 815E support PC133 SDRAM and finally give a choice to mainstream users who want extra speed but don't want to pay Rambus's high premium. To shore up its 820 chip set line and satisfy high-end users, Intel has brought out the 820E, which lacks the memory problems of previous 820s.

Like the older 810 and 810E chip sets, the 815 and 815E have integrated graphics. That design saves money but, in the case of the 810s, left you with no real upgrade options. That's not true of the 815s. With those chips, PC vendors can offer three levels of graphics quality: standard integrated, integrated with a 4MB 3D graphics accelerator, and with a 4X AGP slot for a third-party graphics card.

Expect the 815 and 815E in midrange PCs from major vendors such as HP and Micron's ClientPro Cns, for example, will feature the 815E in a standard configuration with a Pentium III-667, 128MB of RAM, a 15GB drive, the 4MB 3D graphics accelerator, a 17-inch monitor, and Windows 2000. It will list for $1499. Look for other vendor announcements later this summer and fall.

The Rambus-only 820E lacks the memory translator hub that caused the recent recall of previous 820 SDRAM-based boards. It also features a new I/O Controller Hub 2, or ICH2, which replaces the 820's original ICH. The ICH2 supports high-end features such as the fast ATA/100 hard drive standard (up from ATA/66), full six-channel stereo sound (up from two channels), and four USB ports (up from two). The ICH2 also supports three integrated LAN options: two 10/100 ethernet options, and a 1-mbps home phone line alternative. It also offers a more flexible add-in solution for cards based on the Communication and Networking Riser specification. Like the 820E, the 815E includes the ICH2, while the lower-priced 815 uses Intel's original ICH.

No major vendors are expected to offer 820E PCs at the chip set's launch; you should see them in high-end PCs this fall.

The 815 chip set should have a long, successful life. The 820E, however, won't reside at the top for long. Intel's next-generation, 1-GHz-plus Willamette processor, expected in the second half of the year, will use a new chip set, code-named Tehama.

--Tom Mainelli

Memory Unmuddled

DDR SDRAM: Double Data Rate SDRAM, an upcoming system RAM technology, borrows a technique from RDRAM to double SDRAM's data-transfer rate to roughly RDRAM speeds.

PC-100 SDRAM: Synchronous DRAM (the workhorse of modern PCs) running at 100-MHz bus speed.

PC-133 SDRAM: Synchronous DRAM running at 133-MHz bus speed.

RDRAM: Rambus DRAM can run about three times faster than typical SDRAM. The current version supports bus speeds between 600 and 800 MHz, and is often identified as PC600, PC700, or PC800.

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