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#Post#: 7--------------------------------------------------
LGA 775 Introduction
By: Lion_Heart Date: October 16, 2012, 11:34 pm
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LGA 775
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 installing technician 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.
The socket has been superseded by the LGA 1156 (Socket H) and
LGA 1366 (Socket B) 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 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 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.
Location Dynamic Static 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.
Type
Chip form
factors
Contacts
FSB protocol
FSB
frequency
266 MHz (1066 MT/s)
333 MHz (1333 MT/s)
400 MHz (1600 MT/s)
Processor
Dimensions
Processors
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)
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