LGA 775 socket: CPUs, chipsets and cooler fit

Why the board matters as much as the socket

On LGA 775 the processor does not contain a memory controller. It talks to a separate northbridge chip over the front side bus, and that chip handles memory and graphics. The bus speed rose over the years, from 533 MT/s on early Celeron D chips to 1333 MT/s on mainstream Core 2 models, and a board has to support the speed that the processor was designed for.

That design explains why compatibility varies so much between boards that all carry the same socket. A board for early Pentium 4 chips may not recognise a Core 2 processor, and a quad core chip draws more current than the voltage regulator of a budget board may be able to supply. The BIOS must also know the processor. Read the maker's support list down to the stepping when you buy a used part.

Memory

The chipset, and not the processor, decides the memory type. Early boards used DDR, most Core 2 era boards used DDR2, and some later boards were built for DDR3. Each board has one kind of slot, and the modules are not interchangeable between types. Open the board's manual before ordering memory for it.

Cooler mounting

LGA 775 coolers mount on holes spaced 72 mm apart, which differs from the 75 mm pattern used by Intel's later sockets from LGA 1156 onward. Intel's boxed coolers of the period locked in with four push pins that pass through the board. Many modern aftermarket coolers do not include an LGA 775 bracket, so check the cooler maker's compatibility list before buying one for an old system.

A processor from this era such as the Intel Core 2 Quad Q6600 has a thermal rating of 95 W or 105 W depending on the stepping, so a cooler of modest size is enough when airflow is reasonable.