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AMD Announces 8-Core Bulldozer CPU

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You can't say that AMD is ever boring. The company says its next-generation Bulldozer CPU core will take a unique approach to computing that goes beyond Hyper-Threading, which some believe could offer phenomenal performance.

Bulldozer makes a fairly big break from how today's multicores are constructed. Today's dual-, quad-, and hexa-cores are based on single-cores strung together. They can share L2 or L3 cache, but generally are partitioned off from each other. With Bulldozer, the basic building block of a multi-core chip changes from a walled off single core to more of a duplex. Two cores are tightly intertwined and share fetch, decode, floating-point scheduler, and dual 128-bit fused-multiply-accumulate units, or FPUs. AMD says each module includes dedicated integer schedulers, pipelines, and L1 cache.


This, AMD says, is far superior to Intel's Hyper-Threading, which can bog down when the same resources are under load.

Hyper-Theading was introduced by Intel in 2002 and takes a single-core and shares its resources by creating a virtual core. In the Pentium 4 days, HT added a 10 to 15 percent performance increase, and in Core i7 chips, performance can be boosted 20 to 25 percent depending on the application.


Just adding dedicated, partitioned cores is a "brute force" approach that wastes resources, AMD says. With its shared resources, Bulldozer can reduce power consumption and shrink the die size, which in turn lowers the cost to produce the chip. AMD says the server version of its Bulldozer chip should deliver 33 percent more cores and a 50 percent increase in "throughput" in the same power envelope as a 12-core Magny-Cours Opteron chip.

"One of the important things here is that Bulldozer is one of the first all-new designs from AMD in a decade," says analyst Nathan Brookwood of Insight 64. Brookwood says one of the more exciting design changes in Bulldozer is its ability to dynamically reallocate resources on single-threaded tasks. On a traditional dual-core, the resources for each walled off core cannot be combined. In Bulldozer, all of the resources of the module can be thrown at it a thread.


"The single-core performance on some floating-point applications is going to be mind-boggling," Brookewood says.


AMD officials say Bulldozer is being targeted at servers and performance desktop machines. The good news is that Bulldozer will be drop-in compatible with most current high-end servers. The bad news is that it won't be compatible with existing AM3 boards. Instead, AMD says it will introduce a new AM3+ socket. These sockets will be backward compatible with older chips so you could drop a Phenom II X6 in it. According to AMD, Bulldozer will be built on a new 32nm process at Global Foundries.


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