Quite a Legacy for Intel’s Tukwila

When Intel released its first microprocessor in 1971, the 4004 processor had 2,300 transistors. Tukwila, the next generation of its Itanium processor due at the end of the year, will have 2 billion.

A lot sure can happen in 37 years.

Tukwila will be the first processor to surpass 2 billion transistors total, thanks to a quad-core design, 30MB of onboard cache and a new interconnect that replaces the frontside bus . Intel claims that Tukwila will double the performance of previous-generation Itanium 9100 processors by adding a modest gain in power consumption.

It’s a pretty ambitious chip, with the new interconnects and RAS features, but it does have an impressive pedigree.

Half of the design team for Tukwila comes from HP’s PA-RISC processor, which was a high-performance RISC chip before HP discontinued it in favor of Itanium; the other half of the team comes from DEC’s Alpha processor.

Alpha was the first 64-bit processor on the market in 1994, but DEC was in decline and never got it off the ground. Compaq bought out DEC in 1998, but it didn’t know what to do with Alpha either. When HP purchased Compaq in 2000, it found itself with two lines of RISC chips it didn’t want.

Intel was happy to take the engineers from both teams.

“In terms of legacy, you got two teams with a lot of experience in designing high-power RISC CPUs, and we were lucky enough to acquire both of them,” Rory McInerney, vice president of the digital enterprise group at Intel, told InternetNews.com.

Tukwila features four cores that run two threads each. To feed eight threads, Intel developed a new interconnect system called QuickPath Interconnect, which will find its way into Nehalem-based Xeons, according to McInerney.

As a result, those Xeons will be able to use the same chipset as the Itanium, saving OEMs money on multiple product lines and a quicker time to market.

More important, though, will be performance.

Tukwila will start at 2GHz, much faster than the 1.5GHz of the current line. The QuickPath interconnects for memory and I/O will mean nine times the I/O bus bandwidth and six times the memory bandwidth of older Itaniums. This will translate to about 96GB per second of throughput at maximum speed.

Nehalem will do away with the frontside bus as well, but QuickPath is meant for just the Itanium and high-end Xeons.

“Feeding the cores is critical, and the QuickPath technology’s goal is to take the memory I/O architecture and design for the next 10 to 15 years, to make sure we continue to scale and meet the demands for performance,” McInerney said.

According to McInerney, while the power draw goes up, it won’t be a major issue. The Itanium 9100 uses about 104 watts of power; the Tukwila will draw 130 watts. Consequently, that 25 percent power bump corresponds to a doubling in performance.

Additionally, “these types of systems tend to have a lot of memory, so the CPU is not a big source of power draw,” he said.

Tukwila will also include new voltage-frequency management. A system may not always need all four cores or eight threads in a CPU, so the circuitry will balance performance and use as needed. If some cores or threads are not being used, they are powered down and extra power is put into cores and threads that do need it, thus increasing performance.

Despite the effort that Intel has put into Tukwila, it has its doubters.

Semiconductor analyst Fred Zieber, president of Pathfinder Research, said he’s skeptical about a 100 percent performance gain until he sees independent benchmarks.

He also said he doubts it will make much difference in the market, anyway.

“I won’t call the Itanium a failure, but it never lived up to its promise in the marketplace,” he said. “It was going to take over the server market and everyone was going to use it, but it was late and performance wasn’t what was expected.”

Part of the issue is that when the Itanium was first conceived, no one expected the x86 architecture to have gained such traction, particularly in the server arena. In terms of numbers, x86 is the dominant player.

Itanium continues to play in the same space as other RISC processors, IBM’s POWER and Sun’s UltraSPARC, at the very high end, where Zieber doesn’t see the market changing significantly.

“All of this is a nice big step — some of it is catch up — but that area of the market … changes very slowly,” Zieber said. “People don’t replace systems wholesale because the software is so difficult to replace. So you don’t expect dramatic changes in the market.”

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