Heading on to Lower Cost
The first Nehalem generation processors for desktop computer systems that belong to Core i7-900 series were based on Bloomfield processor dies. They featured four computational cores, a single 8MB L3 cache, DDR3 memory controller and QPI bus controller. This way, Core i7 processors were unified with the server Xeons, but at the same time caused certain inconveniences when used in desktops. For example, they required triple-channel DDR3 SDRAM, which is not only unusual but even somewhat excessive for desktop use.
As a result, Bloomfield based platform looked as follows:
As for the mainstream solutions, Intel decided to design new semiconductor dies that retain the same key features as the Bloomfield ones, namely, quad-core design and 8MB shared L3 cache memory, but offer more attractive combination of price and features. These “optimized” quad-core processors that also belong to Nehalem generation were codenamed Lynnfield.
I have to point out right away that Lynnfield processors are made with the same 45 nm technology, as Bloomfield processors. Although Intel is planning to implement 32 nm process later this year, they are not going to trial run it on the new CPUs. We should see the products of the new 32 nm process a little later in solutions known as Clarkdale, which should make Nehalem microarchitecture even more affordable for users with limited financial means. So, at first glance the differences between Bloomfield and Lynnfield don’t seem to be too drastic, however, they turn out more than enough to lower the total platform cost almost by half.
As we know, one of the major advantages of Nehalem microarchitecture is modular structure of the processor die that allows the developers to easily change the set of processor functional units without any massive redesign. Intel engineers too advantage of this particular feature when they created their Lynnfield solution. Namely, they first of all replaced the triple-channel DDR3 SDRAM controller with a simpler dual-channel one. Lowering the number of memory channels from three to two doesn’t have that big of an effect on the overall system performance, but directly affects the system cost, because requires fewer DDR3 modules.
They also made one more change towards simplifying the platform, which has been long called for. Obviously, the QPI bus that migrated to Bloomfield solely because of its server roots performs only one function: connecting the CPU with the controller for the PCI Express bus used to connect to the graphics subsystem. So, nothing will really change from a functional standpoint if we remove the X58 IOH chip and QPI bus and replace the QPI controller in the CPU with a PCI Express bus controller. This is exactly what they have done. As a result, systems based on Lynnfield processors can boast the following much simpler structure:
Lynnfield processors have a PCI Express 2.0 bus controller instead of the high-speed QPI bus interface. This controller supports 16 PCI Express 2.0 lanes and allows using either one graphics card or creating dual-card ATI CrossfireX and Nvidia SLI configurations in 8x + 8x mode. Moreover, the CPU acquired low-speed DMI bus connecting the processor with the chipset South Bridge.
As a result, Lynnfield based platform allows not only to give up triple-channel memory in favor of dual-channel one, but also to do just fine without the chipset North Bridge. This certainly helps simplify the mainboard design. And the outcome is quite predictable: not only Intel is going to sell Lynnfield processors at a lower price than the senior ones, but the users will also save some money on memory and mainboards. As a result, it is now possible to fit a Nehalem CPU, mainboard and memory into a sub-$400 budget.
At the same time, it is pretty funny that Lynnfield semiconductor die turned out a little larger in size than a more expensive Bloomfield one: the implementation of a PCI Express controller called for more transistors than the QPI bus controller.
The table below shows how the parameters of these two semiconductor dies compare with one another:
Nevertheless, this difference in die size didn’t prevent Intel from lowering the cost of Lynnfield processors compared with the predecessors. The official Lynnfield prices are going to be from $200 to $555, while different Bloomfield processor models currently range from $285 to $1000.