Intel Turbo Boost, QPI and Triple Channel memory

Intel Turbo Boost

Intel's Nehalem based processors starting at Core i5 600 and upwards incorporate a feature called Intel Turbo Boost technology. Under specific configurations and workloads, Intel Turbo Boost technology enables higher performance by increasing its core frequency.

Intel Turbo Boost technology automatically allows processor cores to run faster than the base operating frequency if the processor is operating below rated power, temperature, and current specification limits. Intel Turbo Boost technology can be engaged with any number of cores or logical processors enabled and active. This results in increased performance of both multi-threaded and single-threaded workloads.

Example: If heavily stressed on all six cores the Core i7 980X will clock to (when properly cooled) 3.46 GHz, that's an extra 133 MHz. However, if just one core is utilized then Turbo Boost can go a little higher, it can increase the base frequency of that core to 3.6 GHz, an additional 266 MHz.

As such, Intel Turbo Boost is very clever in the sense that single threaded applications will get a little extra performance.

Quick Path Interconnect (QPI)

Core i7s sports both the memory controller and system I/O integrated onto the CPU die and therefore eliminates the Intel Front Side Bus (FSB) altogether. The FSB is replaced with one or more high speed, point-to-point buses called the Quick Path Interconnect (QPI), formerly also known as Common Serial Interconnect Bus or CSI.

QPI features mugh higher bandwidth than the traditional FSB and is better suited for system scaling. We quickly close one eye and hint you towards AMD. See, AMD's HyperTransport links are somewhat similar to what Intel is doing today, high-speed point-to-point inter-component or processor connectivity/communications. Intel was tied to the front side bus, which started to interfere with performance. The QPI architecture allows Intel to connect tri- or even quad-channel memory directly to the the processor's integrated memory controller.

Intel also added PCI Express links directly onto the CPU die. This will for sure deliver much more bandwidth for high performance graphics cards and remove any bottleneck issues with other system components. Paired with the X58 northbridge PCIe 2.0, that allows for two x16 or even four x8 PCIe configurations. Plenty to go around, especially with the added rise of USB 3.0 and SATA6G controllers in mind.

QPI is one of the new extendable building blocks of the Nehalem CPU architecture. Gulftown has two QPI links operating at 6400 MT/sec.

QPI uses up to 6400 MT/s (million transfers per second) links on the top-range products, and as shown today, on the 980X processor. Above, a die shot of the Core i7 980X, with a text overlay describing what each segment is.

Triple channel memory controller

With the arrival of Core i7 we learned about on-CPU integrated memory controllers for DDR3 SDRAM with one to three 64-bit memory channels (physically inside the memory controller there's actually support for four, but only three are active though), this is what we call the triple-channel memory controller. As such the total memory bus width goes up from 128-bits to 192-bits, allowing a massive bandwidth increase. Intel eliminated those 'FSB' slowdowns by designing Nehalem's architecture to use 64-bit memory controllers which are connected directly with the processor's silicon. As a result, this new design should bring a bandwidth utilization of as much as 90%, a nice jump from the 50-60% utilization of the older FSB for sure.

The embedded controller of course supports both registered (server market) and unregistered (consumer) memory DIMMs. The controller is fast, very fast, and supports DDR3-800, DDR3-1066, DDR3-1333 JEDEC standards, yet has room for future scalability.

The memory controller itself is able to handle 64GB/s, a full tri-channel DDR3-1333 implementation will only amount to 32GB/s maximum bandwidth utilization. Do the math and conclude that even DDR3-2000 will not max out the controller.

Gulftown by the way is advertised to support up-to DDR3 1066 MHz. In this review we'll be using 2133 MHz OCZ Blade DDR3 memory. It is memory based on Elpida's HYPER ICs.