LGA 775

Socket T

Type	LGA
Chip form factors	Flip-chip land grid array
Contacts	775
FSB protocol	Quad-Pumped
FSB frequency	533 MT/s, 800 MT/s, 1066 MT/s, 1333 MT/s, 1600 MT/s
Processors	Intel Pentium 4 (2.66 - 3.80 GHz) Intel Celeron D (2.53 - 3.6 GHz ) Intel Pentium 4 Extreme Edition  (3.20 - 3.73 GHz) Intel Pentium D (2.66 - 3.60 GHz) Intel Pentium Extreme Edition  (3.20 - 3.73 GHz) Pentium Dual-Core (1.40 - 2.40 GHz) Intel Core 2 Duo (1.60 - 3.16 GHz) Intel Core 2 Extreme (2.66 - 3.00 GHz) Intel Core 2 Quad (2.40 - 3.00 GHz) Intel Xeon (1.86-3.00 GHz) Intel 'Core' Celeron (1.60 - 2.00 GHz)
This article is part of the CPU socket series

Socket T, also known as LGA775, is Intel's latest desktop CPU socket. LGA stands for Land Grid Array. The word "socket" is now a misnomer, because an LGA775 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 4 cores, as well as the Smithfield and Presler Pentium D cores, currently use the LGA775 socket type. In July 2006, Intel released the desktop version of the Core 2 Duo (codenamed Conroe), which also uses this socket, as does the subsequent Core 2 Quad. Intel changed from Socket 478 to LGA775 because the new pin type offers better power distribution to the processor, allowing the front side bus to be raised to 1600 MT/s. The 'T' in Socket T was derived from the now cancelled Tejas core, which was to replace the Prescott core. As it is now the motherboard which has the pins, rather than the CPU, the risk of pins being bent is transferred from the CPU to the motherboard. 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 mechanism placed on top of the CPU.

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 sink 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 Socket T, 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 478. This was done to avoid the reputed danger of the heatsinks/fans of pre-built computers falling off in transit. LGA775 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 4 CPUs, and this initially neutralized the benefits of better heat transfer. However, modern Core 2 processors run at lower temperatures than the Prescott CPUs they replace.

Socket T mechanical load limits

All socket T processors (Pentium 4, Celeron, Core 2 (and extreme) and Quad Xeon) have the following mechanical maximum load limits which should not be exceeded during heatsink 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)	311 N (70 lbf)

The transition to the LGA packaging has lowered those load limits, which are smaller than the load limits of Socket 478 processors but they are bigger than Socket 370 and Socket A processors which were fragile. They are large enough to ensure that processors will not crack.

Chipsets for Socket T

Intel: iE7221, iE7230W, i3200/3210, 845GV(e.g:Asrock 775i45GV), 848P, 865 series, 875p(e.g:DFI Lanparty 875P-T ), 915 series, 925X/XE, 945 series, P/G965, Q963, 975X, P/G31, G33, G35, P35, X38, Q35, X48, P45 (coming).

nVidia: nF4i, 570i, 610i/GF7050, 630i/GF7150, 650i, 680i, 750i, 780i, 790i

VIA: P4M800, P4M890, P4M900, PT880U, PT890

SiS: 649, 661FX, 662MX, 671, 672FX

ATi: Xpress 200i/1150i, Xpress 1250i, Xpress 3200i

See also

• List of Intel Pentium 4 microprocessors
• List of Intel Core 2 microprocessors