LGA775

CPU socket
name = LGA775


formfactors = Flip-chip land grid array | contacts = 775
type = LGA
protocol = Quad-Pumped
core bus = 133MHz, 200MHz, 266MHz, 333MHz
fsb = 533 MT/s, 800 MT/s, 1066 MT/s, 1333 MT/s, 1600 MT/s
voltage =
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 - 3.33 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)

LGA775, also known as Socket T, 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). [cite web|url=http://www.asisupport.com/ts_training_LGA775.htm|title=New P4 Socket Type LGA775 (Socket T)|accessdate=2007-03-14|publisher=asisupport.com]

The Prescott and Cedar Mill Pentium 4 cores, as well as the Smithfield and Presler Pentium D cores, used 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 canceled Tejas 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 LGA775 which is used for consumer level desktops and LGA771 used for (Xeon based) workstation and server class computer 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 LGA775 specifications,but from the information available appear to be consistent with those of LGA771. Considering that LGA775 predated LGA771 by nearly a year and a half,it would seem that LGA771 was adopted from LGA775 rather than the other way around.

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 LGA775, 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. 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.

LGA775 mechanical load limits

All LGA775 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.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.

Chip sets for LGA775

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, P43, P45.

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

ee also

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

References