Intel Lynnfield Core i5-750 & Core i7-870 Processor Review

by MAC     |     September 6, 2009

Microarchitecture Dissected

In 2007, Intel unveiled the Tick-Tock Model as a demonstration of the company's dedication towards continued rapid technological innovation. The "tick" is a shrinking of the previous architecture manufacturing process (65nm --> 45nm --> 32nm) and the "tock" is a new architecture. Since Penryn was a shrink and slight improvement of the preceding Core architecture, it was time for a brand new architecture and that is where Nehalem came in last November. Lynnfield remains a Nehalem part, since it is neither a new architecture, nor does it feature a smaller manufacturing process. Lynnfield is simply a new core variant based on the Nehalem architecture.

Bloomfield die on the left, new Lynnfield die on the right.

On the left we have the current "Bloomfield" die, which was Intel's first native quad-core design, unlike Core 2 Quad models which are effectively two dual-core dies mounted in one CPU package. The Bloomfield and Lynnfield dies are obviously quite similar. Same number of cores, same size L1/L2/L3 cache size, system request queue (used for inter-core communication), similar integrated memory controller (IMC), etc. However, Lynnfield does away with Bloomfield's two QuickPath Interconnects (QPI), has one less 64-bit DDR3 memory channel, and most importantly features an industry-first integrated PCIe controller, which support 16 PCIe 2.0 lanes. Can you say ultra-low latency CPU-GPU communication?

In quantifiable terms, the die size of the Lynnfield processors is 296mm˛. By comparison, the Bloomfield measures 263mm˛, while the Core 2 Quad "Yorkfield" die is 214mm˛. Lynnfield clocks in at 774 million transistors, which is 43 million more than Bloomfield (731M.), but still less than Yorkfield, which had 820 million transistors due to its large and extremely transistor dense 12MB L2 cache. All three cores are manufactured using the same 45nm High K + metal gate transistor technology.

Now many of you are probably looking at the die pictures and saying "It is pretty but what am I looking at exactly?". A valid question, so let's take a look at the Lynnfield core layout:

As you can see, the integrated PCIe controller takes up a big chunk of the die, and it definitely explains why Lynnfield has 43 million more transistors than the Bloomfield core.

Part of the reason that Intel was able to design and manufacture Lynnfield so quickly is because the Nehalem architecture is dynamically scalable, and it was designed with modularity in mind. What this means is that Intel can custom create processors based on the needs of the market without having to go design a brand new chip from scratch. They can add or remove cores, L3 cache, number of QPI links, number of memory channels, type of memory supported, power management, and even integrated graphics. Therefore, Intel have the ability to add new blocks to the core without having to go to the drawing board and redesigning the whole layout. Basically, they are only limited by how much stuff they can actually fit on one CPU package. Think of it as a multi-million dollar Lego set.

In the following page, we will examine some of the more functional features and technologies that Intel have built into the Core i5-750 and i7-860/870 processors.

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