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Drilling into dual core

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Dual-core

Matthew Broersma ZDNet.co.uk

Published: 28 Sep 2005 17:25 BST

The microprocessor industry is going through a major technological shift that will have big implications for PC and server makers, software vendors and, not least, those buying the technology. The transition will see two or more processor cores placed on a single die, a strategy first put into practice by mass-market chipmakers this spring; by the end of next year, nearly all the chips sold by Intel and AMD will be dual-core.

Hardware makers are taking pains to reassure customers that the shift to dual-core is nothing out of the ordinary — just the latest design technique for keeping processor performance on the rise. But dual-core and multicore chips are leading to wider changes in the way hardware is designed, what performance users can expect from it and the way software is licensed.

Dual-core is part of a wider industry trend away from reliance on processor clock speed as the main driver of performance. High-end Unix servers moved away from clock speed years ago, shifting to more efficient RISC processors and, starting in 2000, dual-core chips. In 2001 AMD jumped on the bandwagon, arguing that ratcheting up chip frequency — known as frequency scaling — was offering diminishing returns.

AMD began using a more efficient chip design and stopped using clock speed in its marketing materials, instead offering model numbers that gave a performance estimate. Following this path led AMD to offer its 64-bit extended instruction set, and, in April of this year, its first dual-core Opterons for servers and workstations. Dual-core Athlon desktop chips arrived in May.

Intel stuck with frequency scaling much longer, producing chips that ran at higher and higher frequencies, sucked up more power and produced more heat. Finally, however, Intel was forced to admit that a more efficient approach was needed. The company tore up its roadmap, killing a planned chip called Tejas, and coming up with a new strategy that had dual-core as its centre-piece.

"Intel is going multi-core because it needed a competitive response to the AMD strategy," says Peter Glaskowsky, an architect with Silicon Valley microprocessor start-up MemoryLogix and analyst for Envisioneering. "Tejas was so big, complex and hot that Intel had to kill it."

Intel's first dual-core chip, the Pentium D, came out in April for desktops and July for low-end, single-processor servers. The company now has 17 multicore projects in development, and says more than 85 percent of its chip sales will be multi-core by the end of next year. (AMD's estimate is slightly higher, at 90 percent.) The first dual-core Itaniums are to appear by the end of the year, as are the first dual-core Xeons, originally planned for 2006.

On top of that, Intel is rolling out a new architecture designed to replace the NetBurst system behind the Pentium 4, and to unify its laptop, desktop and server lines. The new architecture and its surrounding platforms will be based on multicore chips and inspired by the integrated approach of Centrino.

At first glance, the benefits of multicore seem straightforward. The new chips are designed to allow seamless upgrades from single-core processors, with just a BIOS update. The design means each chip can run at a lower frequency, so that heat and power requirements stay the same — but with a surprising jump in performance. In one case, a dual-core Opteron system showed a performance improvement of more than 80 percent for a SAP application environment, according to HP, though most affected applications will see gains more like 40-50 percent.

Customers have paid attention, and are already lining up to buy dual-core systems. Since AMD was first off the block, it has benefited most so far, taking more than 11 percent of x86 server shipments in the second quarter of 2005, up from about 7 percent in the first quarter, says Mercury Research. AMD has never before passed the 10 percent mark for server shipments.

New, smaller manufacturing processes made dual-core chips practical about five years ago, but power management has only more recently become a major issue for enterprises. That's partly because of the rise of dense server installations, particularly blade servers. "These dense technologies we had developed actually created a different issue for us, which was how do you power these, how do you cool them, how do you ensure these systems operate effectively?" says Phil McLean, HP's UK server product manager.