PC memory: The next great battle?

PC memory technology is outdated. Now two rival technologies are vying to make your computer faster, but which will win?
Written by John G.Spooner, Contributor

The computer industry is famous for its battles -- Macintosh vs PC, Intel vs AMD, Windows vs Linux. Now get ready for the next great fight: PC memory.

This war is over how personal computers handle system memory, an arcane but critical technology that affects overall performance. Already, chip titans Intel and Advanced Micro Devices (AMD) are lining up in opposing camps, ensuring that the war could be long, bloody and divisive.

The technologies at the centre of the debate are Rambus direct RAM and double data rate DRAM (DDR). Both are the contenders to replace synchronous dynamic RAM (SDRAM) as the mainstay PC memory technology.

In short, both memory technologies were developed to allow PC systems to keep up with the rapid increase in processor clock speeds. Even as processors get faster, they will eventually hit a bottleneck because the data flowing through the system can't keep up the same pace.

DDR DRAM, pioneered by a consortium of chip makers and embraced by AMD, promises to more than double the available memory bandwidth of a PC, and for a very small price premium. It is expected to begin production in the second half of 2000 at a price premium of only seven to 10 percent above the memory technology now in use. DDR could reach price parity with SDRAM in the first half of next year.

But DDR is playing catch-up with memory technology developed by Rambus, which has been available since November. Rambus commands a huge price premium -- PC manufacturers using the technology pay more than 300 percent more than the price of SDRAM, based on prices Dell Computer charges for systems with Rambus and with SDRAM.

Despite the high cost and several company misfires -- a production delay caused Intel to push back introduction of its 820 chipset -- the chip giant continues to back Rambus. (Intel has said, however, that it will support DDR for server products.)

Investors are also in love with Rambus. Morgan Stanley Dean Witter analyst Mark Edelstone set a 12-month price target of $500 (£310) a share, citing Intel's loyalty to the technology. Rambus this week was trading at about $350 (£217). AMD is on the other side of the trench, occupied by DDR. Like Rambus, DDR doubles system memory bandwidth, thus increasing overall PC performance. Both memory technologies were developed to allow PC systems to keep up with the rapid increase in processor clock speeds.

There will actually be two flavours of DDR to start. The first, PC 1600, will offer a bandwidth of 1.6GB per second -- twice as much as today's standard 100MHz SDRAM memory. The second kind, PC 2100, delivers 2.6GB per second of peak bandwidth. Rambus delivers 1.6GB of peak bandwidth, while the current peak bandwidth of SDRAM is 800MB per second.

"DDR, fundamentally, is a two-times improvement over SDRAM at the same clock speed," said Mark Kellogg, a senior member of the staff at IBM Microelectronics.

DDR derives its increase over SDRAM by transmitting data on both edges of a clock cycle, moving twice as much data per given clock speed, he said. However, since DDR and SDRAM are based on the same underlying technology, "You're not going to have to pay for the ramping and development," Kellogg said.

IBM this week put its weight behind DDR, announcing it will utilise it in all of its servers when the technology becomes available. But IBM is interested in DDR for more than servers: It has designed DDR memory modules, known as DIMMs, or dual inline memory modules, that will be included in all its PCs and servers.

The bottom line for PC makers and memory manufacturers may be that DDR offers the path of least resistance. Besides cost advantages, there is technology momentum behind it in the PC graphics market. Graphics board makers, such as nVidia, use DDR in their products.

The other advantage to DDR is the licensing model -- or the lack thereof. Memory makers must purchase a licence from Rambus in order to make the memory, a cost that eats into profits. By contrast, DDR is a freely available specification hammered out by a technology standards committee of memory manufacturers, called JEDEC Solid State Technology Association.

DDR's story may become even more compelling shortly. While IBM pushes the technology for servers, AMD will be DDR's biggest proponent for desktop PCs and workstations. The company is working on a pair of chipsets that will support DDR and raise bus speeds to match. "It's the availability of chipsets that will determine the success of (DDR) in the desktop space," predicted IBM's Kellogg.

The decision to support DDR over Rambus was simple, said Bryan Longmire, AMD product marketing manager. "Our OEMs said, we want to increase memory bandwidth, but we want to do it on the same cost curve. Consumers will benefit, too. You can initially double memory bandwidth for similar, if not equal cost," he added.

AMD's forthcoming 760 chipset for single-processor PCs will support a 200MHz or 266MHz system bus, to match both 200MHz and 266MHz DDR modules. The AMD 770 chipset will do the same, but for dual-processor machines.

For the moment, the technologies will not be compatible -- Rambus won't run with AMD chips (although AMD has a Rambus licence), and DDR won't run with Intel. However, chip manufacturer VIA Technologies is developing a chipset that will allow PC makers to use DDR memory with Intel chips. If PC makers follow the logic AMD expects them to, this chipset should be popular as well.

Intel has bet heavily on Rambus, saying it is the right technology for high-performance desktop PCs. To support that boast, it is pairing Rambus with forthcoming processors including its high-end PC chip, codenamed Willamette, and the low-cost processor, codenamed Timna. The two chips are expected in the second half of the year. Timna, however, will support SDRAM to start.

Also, although Rambus is in greater supply now than it had been at introduction, only Dell Computer is shipping in any quantities, analysts said. Hewlett-Packard and Compaq Computer have announced support, but have yet to ship any quantities.

Despite their relative advantages or disadvantages, analysts say it is too early to count Rambus out or DDR in. "The next three to four months will be critical," said Mike Feibus, principal analyst at Mercury Research. "The memory suppliers are not all bought in (to Rambus)."

When it comes to the ultimate success or failure of Rambus memory, analysts say that chipsets will play a major role. Intel's forthcoming 815 chipset, which has the ability to span a wide range of Pentium III systems -- from mid-range right up to high-end 1GHz PCs -- could replace the 820 chipset, which supports Rambus, analysts say. "Some of the OEMs are looking at that as a top-to-bottom Pentium III platform. If it takes hold, that could relegate the 820 and Rambus to niche status," Feibus said.

Indeed, ZDNet US reported earlier this week that Compaq is looking at doing just that with its DeskPro line of commercial PCs. Feibus said, "The 815 could help bring [Rambus] prices more in line and make it more acceptable," he said. "It's too soon to tell."

The bottom line, he said: "Rambus is still really expensive."

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