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Desktop Platform Refresh

With the launch of the new microarchitecture AMD not only kept the design of the new platform, but even maintained compatibility of the new Bulldozer processors with the existing infrastructure. As a result, just like their predecessors, the new processors contain an integrated North Bridge with the L3 cache, memory controller and Hyper-Transport bus controller. At the same time although all recently launched AMD and Intel processors also have an integrated PCI Express graphics bus controller, the new Bulldozer doesn’t have it.

Just like processors based on K10 microarchitecture, the North Bridge in Bulldozer processors works at its own clock frequency, which is set at 2.0-2.2 GHz for different CPU models. Note that this frequency does have some effect on performance, because it directly affects the speed of L3 cache. And as we have already said, the new processors have an 8 MB L3 cache with 64-way associativity. Per special request from the corporate users, the data stored in this cache-memory is protected with error correction code (ECC).

The memory controller in the Bulldozer processors doesn’t boast anything principally new. Just as before, it supports DDR3 SDRAM, uses dual-channel design and in fact consists of two independent single-channel controllers that may work as a pair or independently. The only thing AMD added here is the support for faster memory types, such as DDR3-1867, and compatibility with energy-efficient memory modules working at 1.25 V and 1.35 V.

Speaking of the desktop Bulldozer modification codenamed Zambezi, we should mention that it is designed for the new Socket AM3+ platform also known as Scorpius. Socket AM3+ has 942 pins, which is 1 pin more than Socket AM3 has. However, despite the pin difference the new Zambezi will be compatible with the old Socket AM3 mainboards, too. If you use a new processor with the old mainboard, you will only lose some selected power management functions. For example, the frequencies will switch slower with active Turbo Core and Cool’n’Quiet and Vdrop will not work at all.

Nevertheless, AMD worked closely with all mainboard manufacturers to make sure that by the time Zambezi launches there will be numerous new products available based on the new chipsets from the 900-series. The flow-chart below shows a typical system built around Zambezi processor and the new chipset:

The distinguishing feature of the new AMD 990FX (and its simpler modifications – AMD 990X and AMD 970) is basically just the support of specific electrical peculiarities of the new Socket AM3+. There are no new interfaces of any kind. Just like the 800-series chipsets, the new South Bridge supports six 6 Gbps ports and fourteen USB 2.0 ports. Even though we were dying to see such things as PCI Express 3.0 or at least USB 3.0 support in the new chipsets, there is nothing like that. It is actually pretty strange because the chipsets for the lower-end Socket FM1 platform did acquire USB 3.0 support.

The only differences between the new chipset modifications are the types of supported multi-GPU configurations:

 
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