LGA 775, also known as
Socket T, is an Intel desktop
CPU socketA CPU socket or CPU slot is an electrical component that attaches to a printed circuit board and is designed to house a CPU . It is a special type of integrated circuit socket designed for very high pin counts...
. LGA stands for
Land Grid ArrayThe land grid array is a type of surface-mount packaging used for integrated circuits. It can be electrically connected to a PCB either by the use of a socket or by soldering directly to the PCB.-Use in microprocessors:...
. The word "socket" is a
misnomerA misnomer is a term which suggests an interpretation that is known to be untrue. Such incorrect terms sometimes derived their names because of the form, action, or origin of the subject becoming named popularly or widely referenced—long before their true natures were known.- Sources of misnomers...
, because an LGA 775 motherboard has no socket holes; instead, it has 775 protruding pins which touch contact points on the underside of the processor (CPU).
The Prescott and Cedar Mill
Pentium 4The Pentium 4 brand refers to Intel's line of single-core mainstream and high-end desktop and laptop central processing units introduced on November 20, 2000...
coresYonah was the code name for Intel's first generation of 65 nm process mobile microprocessors, based on the Banias/Dothan-core Pentium M microarchitecture. SIMD performance has been improved through the addition of SSE3 instructions and improvements to SSE and SSE2 implementations, while integer...
, as well as the Smithfield and Presler
Pentium DThe Pentium D brand refers to two series of desktop dual-core 64-bit x86 processors with the NetBurst microarchitecture manufactured by Intel. Each CPU comprised two dies, each containing a single core residing next to each other on a multi-chip module package. The brand's first processor,...
cores, used the LGA 775 socket.
LGA 775, also known as
Socket T, is an Intel desktop
CPU socketA CPU socket or CPU slot is an electrical component that attaches to a printed circuit board and is designed to house a CPU . It is a special type of integrated circuit socket designed for very high pin counts...
. LGA stands for
Land Grid ArrayThe land grid array is a type of surface-mount packaging used for integrated circuits. It can be electrically connected to a PCB either by the use of a socket or by soldering directly to the PCB.-Use in microprocessors:...
. The word "socket" is a
misnomerA misnomer is a term which suggests an interpretation that is known to be untrue. Such incorrect terms sometimes derived their names because of the form, action, or origin of the subject becoming named popularly or widely referenced—long before their true natures were known.- Sources of misnomers...
, because an LGA 775 motherboard has no socket holes; instead, it has 775 protruding pins which touch contact points on the underside of the processor (CPU).
Technical Specifications
The Prescott and Cedar Mill
Pentium 4The Pentium 4 brand refers to Intel's line of single-core mainstream and high-end desktop and laptop central processing units introduced on November 20, 2000...
coresYonah was the code name for Intel's first generation of 65 nm process mobile microprocessors, based on the Banias/Dothan-core Pentium M microarchitecture. SIMD performance has been improved through the addition of SSE3 instructions and improvements to SSE and SSE2 implementations, while integer...
, as well as the Smithfield and Presler
Pentium DThe Pentium D brand refers to two series of desktop dual-core 64-bit x86 processors with the NetBurst microarchitecture manufactured by Intel. Each CPU comprised two dies, each containing a single core residing next to each other on a multi-chip module package. The brand's first processor,...
cores, used the LGA 775 socket. In July 2006, Intel released the desktop version of the
Core 2 DuoCore 2 is a brand encompassing a range of Intel's consumer 64-bit x86-64 single-, dual-, and quad-core CPUs based on the Intel Core microarchitecture. The single- and dual-core models are single-die, whereas the quad-core models comprise two dies, each containing two cores, packaged in a multi-chip...
(codenamed Conroe), which also uses this socket, as does the subsequent Core 2 Quad. Intel changed from
Socket 478Socket 478 is 478 contact CPU socket used for Intel's Pentium 4 and Celeron series CPUs. Socket 478 was phased out with the launch of LGA 775.-Technical specifications:...
to LGA 775 because the new pin type offers better power distribution to the processor, allowing the
front side busIn personal computers, the front side bus is the bus that carries data between the CPU and the northbridge.Depending on the processor used, some computers may also have a back-side bus that connects the CPU to the cache...
to be raised to 1600
MT/sTransfer or the more common derivatives Gigatransfer and Megatransfer are terms used in computer technology, referring to a number of data transfers . They are most commonly used for measuring transfer rates...
. The 'T' in Socket T was derived from the now canceled
TejasTejas was a code name for Intel's microprocessor which was to be a successor to the latest Pentium 4 with the Prescott core. Jayhawk was a code name for its Xeon counterpart...
core, which was to replace the Prescott core.
Another advantage of this newer architecture is that it is now the motherboard which has the pins, rather than the CPU, transferring the risk of pins being bent from the (usually more expensive) CPU, to the (typically less expensive) motherboard. Furthermore, the risk of bent pins is reduced because the pins are spring-loaded and locate onto a surface, rather than into a hole. Also, the CPU is pressed into place by a "load plate", rather than human fingers directly. The installing technician lifts the hinged "load plate", inserts the processor, closes the load plate over the top of the processor, and pushes down a locking lever. The pressure of the locking lever on the load plate clamps the processor's 775 copper contact points firmly down onto the motherboard's 775 pins, ensuring a good connection. The load plate only covers the edges of the top surface of the CPU. The center is free to make contact with the cooling device placed on top of the CPU.
An examination of the relevant Intel data sheets show that LGA 775 which is used for consumer level desktops and LGA 771 used for (Xeon based) workstation and server class computers appear to differ only in the placement of the indexing notches and the swap of two address pins. Many pins devoted to functions such as interfacing multiple CPUs are not clearly defined in the LGA 775 specifications, but from the information available appear to be consistent with those of LGA 771. Considering that LGA 775 predated LGA 771 by nearly a year and a half, it would seem that LGA 771 was adopted from LGA 775 rather than the other way around.
The socket has been superseded by the
LGA 1156LGA 1156, also known as Socket H, is an Intel desktop CPU socket. LGA stands for Land Grid Array.LGA 1156 is very different from LGA 775, the socket it replaces. LGA 775 processors were connected to a northbridge using the Front Side Bus. With LGA 1156, the features that were traditionally on a...
and LGA 1366 sockets.
Improvements in heat dissipation
The force from the load plate ensures that the processor is completely level, giving the CPU's upper surface optimal contact with the
heat sinkA heat sink is an environment or object that absorbs and dissipates heat from another object using thermal contact...
or cold-water block fixed onto the top of the CPU to carry away the heat generated by the CPU. This socket also introduces a new method of connecting the heat dissipation interface to the chip surface and motherboard. With LGA 775, the heat dissipation interface is connected directly to the motherboard on four points, compared with the two connections of the Socket 370 and the "clamshell" four-point connection of the
Socket 478Socket 478 is 478 contact CPU socket used for Intel's Pentium 4 and Celeron series CPUs. Socket 478 was phased out with the launch of LGA 775.-Technical specifications:...
. This was done to avoid the reputed danger of the heat sinks/fans of pre-built computers falling off in transit. LGA 775 was announced to have better heat dissipation properties than the Socket 478 it was designed to replace, but the Prescott core CPUs (in their early incarnations) ran much hotter than the previous Northwood-core
Pentium 4The Pentium 4 brand refers to Intel's line of single-core mainstream and high-end desktop and laptop central processing units introduced on November 20, 2000...
CPUs, and this initially neutralized the benefits of better heat transfer. However, modern
Core 2Core 2 is a brand encompassing a range of Intel's consumer 64-bit x86-64 single-, dual-, and quad-core CPUs based on the Intel Core microarchitecture. The single- and dual-core models are single-die, whereas the quad-core models comprise two dies, each containing two cores, packaged in a multi-chip...
processors run at lower temperatures than the Prescott CPUs they replace.
LGA 775 mechanical load limits
All LGA 775 processors (Pentium 4, Celeron, Core 2 (and extreme) and Quad Xeon) have the following mechanical maximum load limits which should not be exceeded during heat sink assembly, shipping conditions, or standard use. Load above those limits will crack the processor die and make it unusable.
| Location |
Dynamic |
Static |
| IHS Surface |
756 N (170 lbf The pound-force or simply pound is a unit of force.- Definitions :The pound-force is approximately equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth...
) (77 kpThe unit kilogram-force or kilopond is defined as the magnitude of the force exerted on one kilogram of mass by a gravitational field . So one kilogram-force is by definition equal to newtons...
) |
311 N (70 lbf The pound-force or simply pound is a unit of force.- Definitions :The pound-force is approximately equal to the gravitational force exerted on a mass of one avoirdupois pound on the surface of Earth...
) (31 kpThe unit kilogram-force or kilopond is defined as the magnitude of the force exerted on one kilogram of mass by a gravitational field . So one kilogram-force is by definition equal to newtons...
) |
The transition to the LGA packaging has lowered those load limits, which are smaller than the load limits of
Socket 478Socket 478 is 478 contact CPU socket used for Intel's Pentium 4 and Celeron series CPUs. Socket 478 was phased out with the launch of LGA 775.-Technical specifications:...
processors but they are bigger than
Socket 370Socket 370 is a common format of CPU socket first used by Intel for Pentium III and Celeron processors to replace the older Slot 1 CPU interface on personal computers. The "370" refers to the number of pin holes in the socket for CPU pins...
and
Socket ASocket A is the CPU socket used for AMD processors ranging from the Athlon Thunderbird to the Athlon XP/MP 3200+, and AMD budget processors including the Duron and Sempron. Socket A also supports the recent AMD Geode NX embedded processors...
processors, which were fragile. They are large enough to ensure that processors will not crack.
See also