How IBM plans to change the chip world

Execs say the debut of Power4 processors will have more of an impact on PC users than the latest 1GHz chips

If you had a hard enough time getting used to the idea that a 1GHz processor would one day power regular computer systems, how does the prospect of 2GHz chips grab you?

That day is not far away. IBM's Enterprise Systems Group is already working on prototypes of its forthcoming Power4 processor, a chip that officials say will boost the performance of high-end servers used for Web hosting and e-commerce.

The Power4 was designed as a server chip for very expensive hardware. But IBM executives say the new line might ultimately have a greater impact on personal computing than recently announced 1GHz desktop PC chips from AMD and Intel, which last week announced their new entries.

"Products like Power4 will have much more of an influence on you as a consumer than having a desktop running at 1GHz," said Dr Joel Tendler, a senior technology architect with IBM's Enterprise Systems Group.

IBM's Power4 is unique in that it can offer multiprocessing from the confines of a single chip. Power4 chips will combine two processors on a single die, which is the slab of silicon on which the processor is built. Power4 is a 64-bit chip, meaning it processes data in 64-bit chunks, as opposed to most desktop chips, which tackle 32-bit data.

Power4 will be included in high-end RS/6000 servers that perform large numbers of online transactions or host high-traffic Web sites, such as those involved with the Olympic Games, Tendler said.

Instead of raw clock speed, he said, "the amount of bandwidth necessary just to accommodate (a site like the Olympics) is going to be high."

Analysts agree that bandwidth, not clock speed, is more important for server performance. "There's clock speed and then there's the power of the computer," said Fred Ziebler, president of Pathfinder Research. "You can compare [Power4] to Pentiums in clock speed, but in reality, it's much more powerful."

Chip designers say that a fast processor isn't much good if a system fails to keep up and feed enough data. Power4's architecture is designed to keep its twin chips well-fed -- it supports a large amount of on-chip Level 2 cache and bus speeds of up to 500MHz between multiple Power4 chips, system input/output and memory.

Level 2 cache increases performance by holding data very close to the chip so that it does not have to reach out across a bus to retrieve it. The buses, which provide data pipelines between the processors or the processors and memory, can carry up to 100GB of data per second.

A single Power4 chip will be made up of 170 million transistors, a large amount of which will probably account for Level 2 cache. It will begin manufacture on IBM's 0.18-micron copper manufacturing process. A micron measures about one-millionth of a metre. Desktop chips, such as Intel's Pentium III, currently use aluminium interconnects.

Copper's advantages over aluminium, among other types of interconnects, are lower resistance, which leads to greater performance, and lower power consumption. Power4 also sports a new design technique called "silicon on insulator", or SOI, which basically cuts down on the amount of capacity inside the processor, also increasing performance.

Power4 is on schedule to ship in the second half of next year in IBM's RS/6000 Unix servers and its AS/400 servers for small and medium-sized businesses running Unix or Linux. Early versions of the chip have their processor cores running at 1GHz each. However, analysts expect the chip to debut at 1.1GHz and scale to 2.0GHz on a 0.13-micron process.

The chip will compete with other high-end, 64-bit processors, including Intel's Itanium and Compaq Computer's Alpha.

AMD is also likely to go down a similar route. As it refines the techniques used to manufacture the Athlon, AMD sees the potential for single-chip multiprocessing, where two Athlons are placed on the same chip. This technology will likely show up in AMD's own 64-bit chip, codenamed Sledgehammer.

The Power4 will also be available in AS/400 systems for small and medium-sized businesses, IBM said.

Now that the gigahertz barrier has been broken, what's next? Will anyone care when we pass 2GHz? Go with Michael Caton and read the news comment about The great microprocessor space race at AnchorDesk UK.

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