Intel Core 2 Quad Q6600 socket: LGA 775

What the Core 2 Quad Q6600 is

The Core 2 Quad Q6600 is a four core processor that Intel released in January 2007 under the codename Kentsfield. It runs at 2.4 GHz and has 8 MB of L2 cache. It has no Hyper-Threading, so four cores means four threads. It was built on a 65 nm process, and it became a popular choice with overclockers after Intel cut its price in April 2007.

It is not a single piece of silicon with four cores. Kentsfield places two dual core dies side by side in one package, each with its own 4 MB of L2 cache. The cores on different dies talk to each other over the front side bus, which is also the path to memory and to the rest of the system. That bus runs at 1066 MT/s on the Q6600.

Intel specified two versions of the thermal rating. Early B3 stepping chips are rated at 105 W, and later G0 stepping chips are rated at 95 W. The G0 version runs cooler, and it is the one to look for when buying a used part.

Socket and motherboard compatibility

The Q6600 goes into an LGA 775 socket, which carries 775 contacts. That is only the first check, because LGA 775 hosted processors from several eras and boards did not all support all of them. Intel's own compatibility listing for the Q6600 names the 3 series and 4 series chipsets, which were released after the processor and were designed for quad core Core 2 chips.

Some older chipsets, including the 965 and 975X families, work with the Q6600 on boards whose makers added support. The conditions were a BIOS update and a voltage regulator that can supply a quad core. A board for an early Pentium 4 will not run it. Always use the maker's CPU support list, find the Q6600 by its stepping and note the minimum BIOS version.

The multiplier is locked at 9, so overclocking meant raising the front side bus. A board with good bus overclocking and a capable voltage regulator mattered more than the chipset family. Memory runs through the chipset as well, so raising the bus speed also changes the memory speed unless the board offers ratios.

Memory, PCIe and cooling

The Q6600 has no memory controller of its own. The northbridge chip on the motherboard handles memory, and the type depends on the board: DDR2 on many boards of 2007 and 2008, DDR3 on some later ones. Open the board's manual before buying memory, because the module types are not interchangeable.

There are also no PCIe lanes on the processor. The chipset provides the graphics slot and the other expansion slots, which is one of the main differences from modern designs where the processor connects to the graphics card directly.

LGA 775 coolers mount on holes spaced 72 mm apart, which is different from the 75 mm and 78 mm patterns used by later Intel sockets. Intel's own boxed cooler used four push pins through the board. Many current aftermarket coolers do not include an LGA 775 bracket, so read the compatibility list first. The CPU cooler compatibility by socket guide covers the patterns.

Upgrade paths

On the same socket the logical upgrade is a 45 nm Yorkfield quad core, which uses less power and runs faster per core, on a board whose maker lists support for it. That is a limited path, because each board model has its own list of supported processors.

Moving off LGA 775 means a new board and new memory. Intel's later mainstream sockets include LGA 1155, and all of them use different processors and different cooler hole patterns.