"Uncore" is a term used by

Intel Intel Corporation is an American multinational corporation and technology company headquartered in Santa Clara, California. It is the world's largest semiconductor chip manufacturer by revenue, and is one of the developers of the x86 seri ...

to describe the functions of a

microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, or a small number of integrated circuits. The microprocessor contains the arithmetic, logic, and control circu ...

that are not in the core, but which must be closely connected to the core to achieve high performance. It has been called "system agent" since the release of the

Sandy Bridge Sandy Bridge is the codename for Intel's 32 nm microarchitecture used in the second generation of the Intel Core processors (Core i7, i5, i3). The Sandy Bridge microarchitecture is the successor to Nehalem and Westmere microarchitecture ...

microarchitecture.

Details

The core contains the components of the processor involved in executing instructions, including the ALU, FPU, L1 and

L2 cache A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, whic ...

. Uncore functions include

QPI The Intel QuickPath Interconnect (QPI) is a point-to-point processor interconnect developed by Intel which replaced the front-side bus (FSB) in Xeon, Itanium, and certain desktop platforms starting in 2008. It increased the scalability and availab ...

controllers,

L3 cache A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, whic ...

, snoop agent

pipeline Pipeline may refer to: Electronics, computers and computing * Pipeline (computing), a chain of data-processing stages or a CPU optimization found on ** Instruction pipelining, a technique for implementing instruction-level parallelism within a s ...

, on-die

memory controller The memory controller is a digital circuit that manages the flow of data going to and from the computer's main memory. A memory controller can be a separate chip or integrated into another chip, such as being placed on the same die or as an int ...

, on-die PCI Express Root Complex, and Thunderbolt controller. Other bus controllers such as SPI and LPC are part of the

chipset In a computer system, a chipset is a set of electronic components An electronic component is any basic discrete device or physical entity in an electronic system used to affect electrons or their associated fields. Electronic components are ...

. The Intel uncore design stems from its origin as the northbridge. The design of the Intel uncore reorganizes the functions critical to the core, making them physically closer to the core on-die, thereby reducing their access latency. Specifically, the microarchitecture of the Intel uncore is broken down into a number of modular units. The main uncore interface to the core is the so-called cache box (CBox), which interfaces with the

last level cache A CPU cache is a hardware cache used by the central processing unit (CPU) of a computer to reduce the average cost (time or energy) to access data from the main memory. A cache is a smaller, faster memory, located closer to a processor core, whic ...

(LLC) and is responsible for managing

cache coherency In computer architecture, cache coherence is the uniformity of shared resource data that ends up stored in multiple local caches. When clients in a system maintain caches of a common memory resource, problems may arise with incoherent data, whi ...

. Multiple internal and external QPI links are managed by physical-layer units, referred to as PBox. Connections between the PBox, CBox, and one or more iMCs (MBox) are managed by the system configuration controller (UBox) and a router (RBox). Removal of serial bus controllers from the Intel uncore further enables increased performance by allowing the uncore clock (UCLK) to run at a base of 2.66 GHz, with overclocking limits in excess of 3.44 GHz. This increased clock rate allows the core to access critical functions (such as the iMC) with significantly less latency, typically reducing core access times to DRAM by 10 ns or more.

References

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External links

Intel Software Developer's Manual. Vol. 3A & 3B
Electrical components Microprocessors