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AMD engineers reveal details about the company's upcoming 45nm processor roadmap, including plans for 12-core processors

"Shanghai! Shanghai!" the reporters cry during the AMD's financial analyst day today. Despite the fact that the company will lay off nearly 5% of its work force this week, followed by another 5% next month, most employees interviewed by DailyTech continue to convey an optimistic outlook.

The next major milestone for the CPU engineers comes late this year, with the debut of 45nm Shanghai. Shanghai, for all intents and purposes, is nearly identical to the B3 stepping of Socket 1207 Opteron (Barcelona) shipping today.  However, where as Barcelona had its HyperTransport 3.0 clock generator fused off, Shanghai will once again attempt to get HT3.0 right.

Original roadmaps anticipated that HT3.0 would be used for socket-to-socket communication, but also for communication to the Southbridge controllers. Motherboard manufacturers have confirmed that this is no longer the case, and that HT3.0 will only be used for inter-CPU communication.

"Don't be disappointed, AMD is making up for it," hints one engineer.  Further conversations revealed that inter-CPU communication is going to be a big deal with the 45nm refresh.  The first breadcrumb comes with a new "native six-core" Shanghai derivative, currently codenamed Istanbul.  This processor is clearly targeted at Intel's recently announced six-core, 45nm Dunnington processor.

But sextuple-core processors have been done, or at least we'll see the first ones this year.  The real neat stuff comes a few months after, where AMD will finally ditch the "native-core" rhetoric.  Two separate reports sent to DailyTech from AMD partners indicate that Shanghai and its derivatives will also get twin-die per package treatment.  

AMD planned twin-die configurations as far back as the K8 architecture, though abandoned those efforts.  The company never explained why those processors were nixed, but just weeks later "native quad-core" became a major marketing campaign for AMD in anticipation of Barcelona.

A twin-die Istanbul processor could enable 12 cores in a single package. Each of these cores will communicate to each other via the now-enabled HT3.0 interconnect on the processor.  

The rabbit hole gets deeper.  Since each of these processors will contain a dual-channel memory controller, a single-core can emulate quad-channel memory functions by accessing the other dual-channel memory controller on the same socket.  This move is likely a preemptive strike against Intel's Nehalem tri-channel memory controller.
 
Motherboard manufacturers claim Shanghai and its many-core derivatives will be backwards compatible with existing Socket 1207 motherboards.  However, processor-to-processor communication will downgrade to lower HyperTransport frequencies on these older motherboards. The newest 1207+ motherboards will officially support the HyperTransport 3.0 frequencies.

Shanghai is currently taped out and running Windows at AMD.


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By xxsk8er101xx on 4/18/2008 8:55:53 AM , Rating: -1
Actually you're technically wrong.

The reason why 32bit apps work in current 64bit OS's is because it emulates 32bit architecture. So 32bit programs running on a 64bit OS runs slower than if it would on a native 32bit OS.


By Jellodyne on 4/18/2008 9:45:54 AM , Rating: 2
You're technically right, but the performance hit is very slight. But there are also times where the address space from a 64 bit Windows OS will cause a 32 bit program to run faster.

See, in most cases under a 32 bit OS, your program is limited to 2GB ram. There's a flag you can set, if the program is written for it, to extend that to 3GB. However, under a 64 bit Windows OS, each 32 bit app can have 4GB of unfettered address space. If you've got more than 2GB of RAM and a memory 32 bit hungry app, the odds are good you'll run faster on 64 bit OS despite the very minor hit from the 32-to-64 translation layer.


By darkpaw on 4/18/2008 9:55:42 AM , Rating: 2
On a fully native 64bit processor like Itanium, you have to emulate the whole 32bit architecture, which comes with a huge performance hit.

On the x64 processors, the entire 32bit architecture is still present. Nothing is actually emulated. A software interface to the 32 bit APIs is provided (Windows on Windows), which is more like virtualization then emulation. This does not cause a significant performance hit.


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