Core i7 is the first Intel processor with an integrated memory controller, feature available on AMD processors since Athlon 64. It is based on Core architecture, like Core 2 Duo and Core 2 Quad, but with several enhancements to increase performance (Nehalem microarchitecture). This CPU family is available in three different sockets, LGA1366 (triple-channel memory architecture and QPI bus), LGA1156 (dual-channel memory architecture, integrated PCI Express 2.0 controller and DMI bus) and PGA988 for laptops (same specs as LGA1156).

Traditionally Intel processors use an external memory controller located in the north bridge chip (also known as Memory Controller Hub, MCH). This means that on CPUs using this architecture the chipset (and therefore, on the motherboard) determines the type and amount of memory you can install on the computer. Since Core i7 memory controller is embedded in the CPU, it's the processor (and not the chipset) who determines which technology and amount of memory you may have installed on your system. The motherboard, however, may impose a limitation on the amount of memory you can install. The memory controller integrated on Core i7 accepts only DDR3 memory (up to 1.6 V, memory modules which require more voltage than this will not work and may even damage the processor). Socket 1366 models support the new triple-channel architecture with DDR3-800 and DDR3-1066 memories, while socket 1156 and 988 models support the now standard dual-channel architecture and DDR3-800, DDR3-1066 and DDR3-1333 memories.

The new triple-channel architecture present on socket 1366 models allows the CPU to access three memory modules at the same time to read or store data, increasing the number of bits that are transferred per clock cycle from 128 (in dual-channel architecture) to 192. In theory, triple-channel architecture offers a 50% bandwidth increase compared to the dual-channel architecture running at same clock rate. For example, DDR3-1066 memories working in dual channel have a maximum theoretical transfer rate of 17 GB/s, while if installed in triple channel they have a maximum theoretical transfer rate of 25.5 GB/s.

Core i7 processors based on socket 1366 communicate with system through a new bus called QPI (Quickpath Interconnect). This bus works at 2.4 GHz (4.8 GB/s) on Core i7 and 3.2 GHz (6.4 GB/s) on Core I7 Extreme. On socket 1156 and socket 988 models the processor has also an embedded PCI Express 2.0 controller, so with these processors the video cards are connected directly to the CPU, what in theory can improve the practical bandwidth achieved. These CPUs can access one video card at x16 transfer rate or two video cards at x8 transfer rate each. Because on these models the PCI Express 2.0 controller is integrated inside the CPU, Intel decided to use a lower speed bus called DMI (Digital Media Interface), which operates at 2 GB/s, to connect the CPU to the chipset; this bus is used to connect the north bridge chip to the south bridge chip on previous chipsets from Intel. The lower bandwidth isn't a problem, as the reason QPI has a high bandwidth is because it is used to connected the CPU to the PCI Express 2.0 controller present on the north bridge chip and since on socket 1156 and socket 988 CPUs this component is inside the CPU an external high-bandwidth bus is not necessary anymore.

Like processors from AMD, Core i7 architecture has a base clock, from which all other clocks are derived. The default base clock is of 133 MHz for all models.

Core i7 features a technology called Turbo Boost, which is an automatic overclocking feature. When the CPU "feels" that more processing power is needed, it increases its internal clock above the labeled clock.

Another interesting feature is that Core i7 supports Hyper-Threading technology, which emulates two logical processors for each processing core. So, since Core i7 has four “real” cores, operating systems detect eight "virtual" cores (threads), i.e. eight processors.

Core i7 Extreme is the most powerful (and expensive) Core i7 model. Their main differences are an unlocked clock multiplier and higher clock speeds for the processor and for the QPI bus (socket 1366 models only).

The main technical features of Core i7 family are:

• Nehalem microarchitecture
• 64 KB L1 cache (32 KB data + 32 KB instruction) per core
• 256 KB L2 cache per core
• 4 MB, 6 MB or 8 MB shared L3 cache memory
• Dual-core or Quad-core technology
• Hyper-Threading (HT) technology
• Socket 1366 or 1156 on desktop models, socket 988 on laptop models
• QPI bus running at 2.4 GHz (4.8 GB/s) or 3.2 GHz (6.4 GB/s) on socket 1366 models
• DMI bus (2 GB/s) on socket 1156 and 988 models
• Integrated memory controller supporting dual-channel architecture (socket 1156 and 988) or triple-channel architecture (socket 1366)
• Support for DDR3 memories up to 1,066 MHz (socket 1366) or up to 1,333 MHz (socket 1156 and 988)
• Integrated PCI Express 2.0 controller on socket 1156 and 988 models (one x16 lane or two x8 lanes)
• Integrated Graphics Adapter on some mobile models
• Turbo Boost technology
• Virtualization technology
• Intel EM64T technology
• SSE4.2 instruction set
• AES-NIS instruction set (32-nm models only)
• Execute Disable Technology
• Enhanced SpeedStep Technology
• 32 nm or 45 nm manufacturing process

A more detailed explanation about Core i7 processors with all differences between Nehalem architecture and the architecture used by Core 2 Duo and Core 2 Quad processors can be seen in our Inside Intel Nehalem Microarchitecture tutorial.

Let’s now take a look on all models launched so far.