Hardware Reference
In-Depth Information
Socket 478 uses a heatsink attachment method that clips the heatsink directly to the motherboard, and
not the CPU socket or chassis (as with Socket 423). Therefore, any standard chassis can be used, and
the special standoffs used by Socket 423 boards are not required. This heatsink attachment allows for
a much greater clamping load between the heatsink and processor, which aids cooling.
Socket 478 processors use five VID pins to signal the VRM built into the motherboard to deliver the
correct voltage for the particular CPU you install. This makes the voltage selection completely
automatic and foolproof. A small triangular mark indicates the pin-1 corner for proper orientation of
the chip.
Socket LGA775
Socket LGA775 (also called Socket T) is used by the Core 2 Duo/Quad processors, the most recent
versions of the Intel Pentium 4 Prescott processor and the Pentium D and Pentium Extreme Edition
processors. Some versions of the Celeron and Celeron D also use Socket LGA775. Socket LGA775,
unlike earlier Intel processor sockets, uses a land grid array format, so the pins are on the socket,
rather than the processor.
LGA uses gold pads (called
lands
) on the bottom of the processor to replace the pins used in PGA
packages. It allows for much greater clamping forces via a load plate with a locking lever, with
greater stability and improved thermal transfer (better cooling). The first LGA processors were the
Pentium II and Celeron processors in 1997; in those processors, an LGA chip was soldered on the
Slot-1 cartridge. LGA is a recycled version of what was previously called
leadless chip carrier
(LCC) packaging. This was used way back on the 286 processor in 1984, and it had gold lands
around the edge only. (There were far fewer pins back then.) In other ways, LGA is simply a
modified version of ball grid array (BGA), with gold lands replacing the solder balls, making it more
suitable for socketed (rather than soldered) applications. Socket LGA775 is shown in
Figure 3.12
.
