At an event today in San Francisco, Intel formally launched its new six-core Xeon 7400 processor, codenamed "Dunnington." The new chip is basically three dual-core Penryn processors packed onto a single processor die, along with a large pool of shared L3 cache and interconnect logic. With six cores and three levels of cache on one die, Dunnington is a 1.9-billion-transistor monster. This is almost as big as the company's latest 2-billion-transistor Itanium chip (launched in February), and it's quite a milestone for the x86 instruction set. In four- and eight-socket configurations, a supercomputer based on the new Xeon can now execute 48 or 96 simultaneous threads per node, a reality that's bound to help the architecture advance further in the high performance computing space. And at the very top end, there's also a 16-socket configuration on offer.
Unlike the 65nm, quad-core Tukwila, Dunnington is produced on Intel's 45nm process. This means that Dunnington uses less power, and indeed, the top-end, 2.66GHz SKU has a 130W TDP (compare Tukwila's 170W TDP). The 2.4GHz part boasts a 90W TDP, and there's a 2.13GHz part that runs at a relatively cool 65W.
The Xeon 7400 family also contains a four-core variant, and since all of the Dunnington floorplans I have seen have six cores, I'm going to speculate that the four-core parts just have one of the core pairs disabled. (This could be done for yield reasons). The family's L3 caches come in 16MB, 12MB, and 8MB variants, with most of them being 12MB.
The Xeon 7400 series architecture
Dunnington is a drop-in replacement for Tigerton on the Caneland server platform, a fact that's actually quite important for the following reason: Nehalem is the successor to Dunnington, but Nehalem will use an entirely different interconnect (QuickPath) than previous x86 designs, which means that Dunnington will have to suffice for users who don't make the jump to QuickPath.
Ultimately, the entire Intel side of the x86 ecosystem will have to shift from the company's existing (and ancient) frontside bus architecture to QuickPath as Intel pushes Nehalem across market segments from the top down. So the six-core Dunnington will provide a kind of "legacy upgrade" path for Xeon users, enabling them to hold out for quite a while before making the QuickPath transition. In this respect, Dunnington's mammoth size and legacy support seem designed to make it a compelling alternative to Nehalem, at least for a quarter or two.Posted on