How the Nehalem Microprocessor Microarchitecture Works

By: Jonathan Strickland

Nehalem Architecture

Intel co-founder Gordon Moore, of Moore's Law fame.
Intel co-founder Gordon Moore, of Moore's Law fame.
Justin Sullivan/Getty Images

You can look at the Nehalem microprocessor as a chip that has two main sections: a core and then the surrounding components called the un-core. The core of the microprocessor contains the following elements:

  • The processors, which do the actual number crunching. This can include anything from simple mathematical operations like adding and subtracting to much more complex functions.
  • A section devoted to out-of-order scheduling and retirement logic. In other words, this part lets the microprocessor tackle instructions in whichever order is fastest, making it more efficient.
  • Cache memory takes up about one-third of the microprocessor's core. The cache allows the microprocessor to store information temporarily on the chip itself, decreasing the need to pull information from other parts of the computer. There are two sections of cache memory in the core.
  • A branch prediction section on the core allows the microprocessor to anticipate functions based on previous input. By predicting functions, the microprocessor can work more efficiently. If it turns out the predictions are wrong, the chip can stop working and change functions.
  • The rest of the core orders functions, decodes information and organizes data.

The un-core section has an additional 8 megabytes of memory contained in the L3 cache. The reason the L3 cache isn't in the core is because the Nehalem microprocessor is scalable and modular. That means Intel can build chips that have multiple cores. The cores all share the same L3 memory cache. That means multiple cores can work from the same information at the same time.


Why create scalable microprocessors? It's an elegant solution to a tricky problem -- building more processing power without having to reinvent the processor itself. In a way, it's like connecting several batteries in a series. Intel plans on building Nehalem microprocessors in dual, quad and eight-core configurations. Dual-core processors are good for small devices like smartphones. You're more likely to find a quad-core processor in a desktop or laptop computer. Intel designed the eight-core processors for machines like servers -- computers that handle heavy workloads.

Intel says that it will offer Nehalem microprocessors that incorporate a graphics processing unit (GPU) in the un-core. The GPU will function much the same way as a dedicated graphics card.

Next, we'll look at the way the Nehalem transmits information.