|Chip form factors||Flip-chip land grid array|
|FSB frequency||133 MHz (533 MT/s)
200 MHz (800 MT/s)
266 MHz (1066 MT/s)
333 MHz (1333 MT/s)
400 MHz (1600 MT/s)
|Processor dimensions||1.47 × 1.47 inches (37.5mm)|
|Processors||Intel Pentium 4 (2.60 - 3.80 GHz)
Intel Celeron D (2.53 - 3.60 GHz )
Intel Pentium 4 Extreme Edition
(3.20 - 3.73 GHz)
Intel Pentium D (2.66 - 3.60 GHz)
Pentium Extreme Edition
(3.20 - 3.73 GHz)
Pentium Dual-Core (1.40 - 3.33 GHz)
Intel Core 2 Duo (1.60 - 3.33 GHz)
Intel Core 2 Extreme (2.66 - 3.20 GHz)
Intel Core 2 Quad (2.33 - 3.00 GHz)
Intel Xeon (1.86-3.40 GHz)
Intel Celeron (1.60 - 2.40 GHz)
This article is part of the CPU socket series
LGA 775, also known as Socket T, is an Intel desktop CPU socket. LGA stands for land grid array. Unlike earlier common CPU sockets, such as its predecessor Socket 478, the LGA 775 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 4 cores, as well as the Smithfield and Presler Pentium D cores, used the LGA 775 socket. 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 LGA 775 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. Another advantage for Intel with 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 CPU to the motherboard. The CPU is pressed into place by a "load plate", rather than human fingers directly. The installer lifts the hinged "weld 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 (processor heatspreader). 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 shows 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 adapted from LGA 775 rather than the other way around.
From i910 to 4X chipset, i910GL/i915G/GL/GV/P/PL/i925X/XE/i945/955/i945G/P/ i955X/i946/946GZ/PL/965/i975/Q965/P965/G965/Q963/i975X/ P35/G35/P33/G33/Q33/P31/G31/X38/X48/P45/P43/G45/G43/G41, all support LGA 775.
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 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 478. 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 4 CPUs, and this initially neutralized the benefits of better heat transfer. However, modern Core 2 processors run at much lower temperatures than the Prescott CPUs they replace.
LGA 775 mechanical load limits 
All LGA 775 processors 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.
|IHS Surface||756 N (170 lbf) (77 kp)||311 N (70 lbf) (31 kp)|
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, Socket 423 and Socket A processors, which were fragile. They are large enough to ensure that processors will not crack.
See also 
|Wikimedia Commons has media related to: Socket 775|
- List of Intel microprocessors
- List of Intel Pentium 4 microprocessors
- List of Intel Core 2 microprocessors
- List of Intel Xeon microprocessors
- "Intel Pentium 4 Datasheet".
- "New P4 Socket Type LGA 775 (Socket T)". asisupport.com. Retrieved 2007-03-14.