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AMD moves to 45-nm with Shanghai

Posted: 26 Dec 2008     Print Version  Bookmark and Share

Keywords:45-nm  server chip  processor  Barcelona processor 

Advanced Micro Devices (AMD) moves to the 45nm technology node with the launch of its new Opteron server chip, code-named Shanghai. AMD is the third manufacturer to reach this milestone after Panasonic and then Intel.

AMD's previous generation 65-nm Barcelona was the industry's first quad-core processor that also included 2MB of shared L3 cache integrated on the same chip with a Northbridge memory controller. The Shanghai chip triples the L3 cache size to 6MB, but all the basic building blocks were already incorporated in the 65-nm Barcelona chip.

A quick glance at the Shanghai chip confirms one of its major selling points. It is pin-for-pin compatible with the Barcelona processor. This approach continues a long-standing AMD strategy to allow server manufacturers to maximise the life of their designs for many generations without new sockets and board redesigns.

Ripping open the chip's packaging offered the first glimpse into whether or not Shanghai was simply a shrink of the Barcelona die layout. Moving to the 45-nm node certainly helped AMD to reduce the die footprint by over 10 per cent to 253 mm2 despite doubling the total SRAM size on the chip from 4 to 8MB. Each of the four processor cores has shrunk by almost 40 per cent to less than 22mm2.

Still, there is no question that Intel is at the cutting edge of process technology. Semiconductor Insights began analysing 65-nm parts from Intel in January 2006. AMD followed up in September 2006 with a dual-core Athlon desktop processor. In addition, Intel introduced its 45-nm high-K metal gate (HKMG) process in November 2007-a year before AMD.

Figure: nFET structure yields 19 per cent better performance.

However, AMD process engineers are quick to point out their strategy of rapidly converting all of its manufacturing volume to the new node after its launch. In terms of architecture, the upcoming introduction of Intel's Nehalem chips will come more than a year later than AMD's design.

Power-saving designs
For servers, we all want our Google results to come fast so speed is important. Intel has a long history of pushing processor speed performance by designing transistors with high on-currents to drive fan-out gates quickly. In fact, Intel's 45-nm HKMG transistors offer the best peak drive currents on the market today with 1.36 �A/�m for nFETs and just over a milliamp for pFETs. Compared to Intel's speed-burners, a typical 45-nm transistor on AMD's Shanghai is a lot less powerful.

But there is more to the story than just pure speed performance. AMD has supplied comparison data that suggests servers based on the Shanghai chip consume up to 15 per cent less power at peak processing load and 30 per cent less at idle than Intel's current 45-nm microprocessor. Data centres need to be kept cool so lowering server chip power reduces the air conditioning load as well. Tally those savings up over many server racks and you begin to add up some real savings.

AMD plans to introduce its version of a HKMG process developed in partnership with IBM midway through 45-nm production. However, AMD's first 45-nm device is manufactured using polysilicon gates with an oxy-nitride dielectric similar to Matsushita's UniPhier video chip-the first to use 45-nm process technology. Just like AMD, Matsushita brought immersion lithography online to meet the scaling requirements of 45 nm. In fact, UniPhier boasts the tightest metal pitches in a logic chip at 138 nm.

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