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Put Dunnington on your desktop

Three Little Penryns and a big, bad pile of cache
Mon Feb 25 2008, 11:25

DUNNINGTON IS the first six-core - single-die, mind you - X86 chip, and the last high-end Penryn derivative before the Nehalems take over. In fact, it is three "little Penryn 3 MB cache" dual core processors put together on the same die, with a huge 16MB L3 cache putting them all together.

This 300+ mm2 behemoth, the largest X86 chip until the 8-core Beckton Nehalems replace it a year or so later, will be a plug-in mPGA604 replacement for the current Tigerton / Caneland platform.

Its large cache should help buffet the relatively slow FSB1066 bus interface on the Caneland quad-FSB chipset, and the core pairs can communicate betwen each other through the much faster L3 cache, rather than that FSB - eliminating quite a bit of that extra FSB traffic in fact.

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Now, Dunnington, at least in this server version, is expected to slow down clock wise a bit to fit into the 130W or so prescribed power envelope. Knowing that Penryns anyway don't guzzle electricity anywhere near their declared figures, I guess it won't be much of a throttle - around 2.8 to 3 GHz is still possible, maybe even 3.2 GHz if the new Penryn steppings prior to Dunnington bring along improved performance per watt.

What if Intel was to repeat its very first Pentium 4 Extreme Edition effort, unveiled to the world first right here and here? At that time, no one expected that Intel would, in a desperate move to stave off Athlon 64, actually repackage its very best large-cache Xeon server chips into the desktops. Then, Extreme Edition meant a really different die (2MB L3 cache extra, for instance) compared to the " classic" desktop CPU.

Can this be done with Dunnington? Say, throw away all the TDP limitation stuff, and plug in one of these hexacore beasts into your fave X48 mobo? What could happen, if the BIOS allows it of course?

Comparing it to Yorkfield is interesting. A single CPU FSB load instead of two like on Yorkfield: in theory, a desktop Dunnington could overclock the FSB quite a bit better - something like stable FSB2000 should not be uncommon. This helps feed the six cores smoothly out of say dual DDR3-2000, or even DDR2-1000, memory channels.

Multi-threaded apps scaling: with the inter-core chat and buzz between the CPUs going through the fast L3 cache now, things like 3DMark06 or CineBench 10 would scale better percentage-wise - something seen on Phenoms, a rare occurence where AMD quad core actually won on something. The huge shared cache would help even more to keep large chunks of code & data in there for such apps. And, the reduced 3 MB per-CPU L2 caches could shave off say two cycles of latency too.

Overclocking: once unlocked, well fed on a good high-end mobo, and even better cooled, this piece of chippery could overclock just as well as the usual Penryns. The three Penryn pieces don't seem to have any critical speed paths between them, as they only talk through the L3. If the heat and power are taken care of we could shoot for 4GHz / FSB 2000 here.

Price - if it delivers on all this, we don't see why Intel could not sell it for $1.5 K a piece. As the Nehalems roll out later, such desktop Dunnington, a six-core ray-traced gaming beast, would keep the X38/48 PC owners happy another year or two. µ

 

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