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Hardware Today — The Power Behind Your Server

By Ben Freeman (Send Email)
Posted Jun 7, 2004


The processor market may drive the server market, but it doesn't always get the same amount of attention. This week, Hardware Today pays the processor space some due, as we zero in on the impact of IBM's POWER5 chip on the 64-bit market and how Big Blue perceives its role.

We look at the processor market, zeroing in on the impact IBM's POWER5 chip is having on the 64-bit space and how Big Blue perceives its role.

IBM released the first two of its long-awaited POWER5-based servers in May: the 2-way i5 520 and the 4-way i5 570. Each POWER5 chip contains two processor cores, providing two processors in one unit, in effect twice as much processing power in the same unit. The 520 and 570 are Dual-Chip Module implementations, on a platform that has a maximum of two POWER5 chips. The 520 has one POWER5 chip, and is a 2-way server. The 570 has two POWER5 chips, and is a 4-way server. .

Down the road, Multi-chip Module (MCM) based POWER5 servers will allow up to 32 chips (with two processor cores each, for a resultant 64-way server), using four Level 3 (L3) cache chips.

Balance of POWER

Ed Broderick, a principal analyst at the Robert Francis Group, sees POWER5 as Big Blue's best balancing act to date. "Whether you're talking cache, processing capacity, or bandwidth, I can't find a single point of weakness or bottleneck in that processor, and that's a marked departure for IBM," he said.

IBM POWER chief scientist Balharam Sinharoy describes the difficulties Big Blue faced to make this possible. "It is a real balancing act, to make sure that you hit the right spot both for commercial applications and for scientific applications," he said. Getting it right, he claims, gave the chip a 40 percent price/performance boost over its POWER4 predecessor.

POWER5 Chip
IBM's POWER5 processor is making waves in the 64-bit world.

POWER5's addition of Simultaneous Multithreading, through which its two processor cores appear on the software level as four logical processors, certainly helped. In addition, increasing the capacity of both the fixed point and floating point registers improved single thread performance and boosted calculation power more than 50 percent, Sinharoy said.

Other enhancements to POWER5 are L2 and L3 caches that are bigger, more accessible, and more closely packed, to offer higher bandwidth. The 1.9 MB on-chip L2 cache is now connected directly to the 36 MB off-chip L3 cache, resulting in less latency. Memory has been packed more densely and given more bandwidth, and POWER5 operates at increased frequencies.

To cram in this additional performance, POWER5 features dynamic power and heat management, through which some transistors are powered down if they won't be needed for currently executing instructions. Without this, "power usage would be very very high," Sinharoy said.

POWER Sharing

"The POWER5 [processor] represents the debut of the Virtualization Engine, which is really going to help to further enable on-demand computing," said Maria DeGiglio, another principal analyst for the Robert Frances Group. The Virtualization Engine, which descends from technology innovations made on zSeries, enables multiple operating systems to use the same hardware in separate logical partitions (LPARs) with each operating system unaware of the others. With Virtualization Engine, POWER5 can dice up a logical partition using as little as one-tenth of a processor core.

Virtualization Engine will find some company on the playing field. "It's going to compete with VMware for certain," said Broderick, adding "IBM can do a more effective job of implementing virtualization because they own the processor, they own the microcode, they own the OS platform, they drive a lot of the middleware."

"It's the old rule too that, if it's on the hardware, it will probably perform better," DeGiglio added.

But Broderick and DeGiglio stress that VMware vs. IBM 's Virtualization Engine is not an either/or proposition. For heterogeneous multivendor environments, IBM's solution will not be pervasive, and Broderick can even imagine a situation where "you're using a Virtualization Engine under the covers, and VMware on top."

POWER Boost

Broderick expects chip production from factories in East Fishkill, NY and Burlington, VT to ramp up quickly in their production efforts. "As IBM increases the yield by a factor of 10x in the next few months. You'll probably see the price drop rather precipitously, making it more attractive to OEM manufacturers," Broderick said.

Sinharoy took a similar, but more reserved, point of view: "Yields were initially low, then as we ramped up and learned the reason for the defects, we started changing the geometry of the design, and we started improving the yield," he said. While he wasn't willing to claim an impeding 10x increase, he did note, "it is true that the yield is going to improve over time."

>> POWER Struggle

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