Processor Types and Specifications - Upgrading and Repairing PCs - page 88

For more information about Socket 370 (PGA-370), Socket 423, Socket A, and Socket
754, see Chapter 3 , “ Processor Types and Specifications ,” of Upgrading and Repairing
PCs, 19th edition , found in its entirety on the DVD packaged with this topic.
Socket 478
Socket 478 is a ZIF-type socket for the Pentium 4 and Celeron 4 (Celerons based on the
Pentium 4 core) introduced in October 2001. It was specially designed to support addi-
tionalpinsforfuturePentium4processorsandspeedsover2GHz.Theheatsinkmounting
is different from the previous Socket 423, allowing larger heatsinks to be attached to the
CPU. Figure 3.9 shows Socket 478.
Figure 3.9 Socket 478 (Pentium 4) showing pin 1 location.
Socket 478 supports a 400MHz, 533MHz, or 800MHz processor bus that connects the
processor to the MCH, which is the main part of the motherboard chipset.
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.