CPU Interfaces and Socket Types

Intel and Advanced Micro Devices (AMD) have many models and qualities of CPUs. Each model is designed to fit into a specific socket on the motherboard. Many pins connect the CPU to the motherboard. Bending (or breaking) even one pin renders the CPU inoperable. A Zero Insertion Force (ZIF) physical interface lets you set the CPU into the array, and then you actuate a lever

to make actual contact. It is imperative to orient the CPU correctly. Usually, there is an obvious guide or indication, like a missing corner pin on the CPU that aligns to a missing hole in the ZIF. Pin Grid Array (PGA) and Staggered Pin Grid Array (SPGA) describe the pin arrangement of the CPU interface with the motherboard. Land Grid Array (LGA) and Ball Grid Array (BGA) refer to processors that use contact-based rather than pin-based connections to the motherboard. Figure 1-2 illustrates a PGA socket, the AMD Socket AM3. Figure 1-3 illustrates an LGA socket, the Intel Socket 1155.

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Figure 1-2 Socket AM3 is designed for AMD processors such as the Phenom II X6.

Figure 1-3Socket LGA 1155 is designed for Intel processors, such as the “Sandy Bridge”second-generation Core i7, Core i5, and Core i3.

6 CompTIA A+ Quick Reference

Tables 1-2 and 1-3 list processors and their associated sockets. Note that some processors are available in models for different sockets.

Table 1-2 AMD Sockets and CPUs

Socket	Supported CPUs
Socket 462 and Socket A	Athlon, XP, XP-M, and MP
	Duron
	Sempron
Socket 754	Athlon 64
	Sempron
	Turion 64
Socket 940	Opteron
	Athlon 64 FX
Socket 939	Athlon 64, FX, and X2
	Opteron
	Sempron
Socket S1	Turion 64, X2
	Athlon 64 X2
	Mobile Sempron
Socket AM2	Athlon X2
	Athlon 64, FX, LE, and X2
	Phenom, X3, and X4
	Sempron and LE
	Opteron and SE
Socket AM2+	Athlon X2 BE
	Athlon 64, FX, LE, and X2
	Phenom, X3, and X4
	Phenom II X2, X3, and X4
	Sempron and Sempron LE
	Opteron and Opteron SE

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Socket	Supported CPUs
Socket AM3 (Socket 941)	Athlon II X2, X3, and X4
	Phenom and Phenom FX
	Phenom II X3, X4, and X6
	Sempron
Socket AM3+	FX 8xxx, 6xxx, 4xxx
Socket F	Opteron
Socket 563	Athlon XP-M
Socket FM1 (BGA-413)	AMD Fusion processors
Socket G34	Opteron MCM 6000-series
Socket C32	Opteron 4000 series
Table 1-3 Intel Sockets and CPUs
Socket	Supported CPUs
Socket 370	Pentium III
	Celeron
Socket 478 and Socket N	Pentium 4, 4 EE, and M
	Celeron
Socket 495	Celeron
PAC418	Itanium
Socket 603	Xeon
PAC611	Itanium 2
Socket 604	Xeon
Socket 479	Pentium M
	Celeron M
	Core Solo and Core Duo
LGA 775 and Socket T	Pentium 4, D, and XE
	Celeron and Celeron D
	Core 2 Duo and Core 2 Extreme

8 CompTIA A+ Quick Reference

Table 1-3 Continued

Socket	Supported CPUs
Socket M	Core Solo and Core Duo
	Core 2 Duo
	Dual-Core Xeon
LGA 771 and Socket 771	Xeon
Socket P	Core 2 Duo, Quad
	Pentium Dual-Core
	Celeron M
Socket 441	Atom
LGA-1156	Core i5
	Core i3
	Pentium Dual-Core
LGA-1155	Core i7
	Core i5
	Core i3
Socket B and LGA 1366	Core i7
	Xeon
	Celeron

CPU Cooling Methods

There are several methods of removing heat from a CPU. The most common solution is an active heat sink: a fan that blows air across a multifinned aluminum or copper assembly fastened firmly to the CPU. The fan is powered by the motherboard, and the hardware monitor feature in the sys-tem BIOS measures fan speed and processor temperature. Many GPUs also have their own cooling fan and heat sink assembly. Figure 1-4 illustrates typical active heat sink assemblies for an AMD Phenom II CPU and an Intel Core i5 CPU.

A thermal compound is used between the heat sink and the CPU. Note that the thermal compound is poisonous and toxic to humans. Use care when applying or removing thermal compound. Note that heat sinks included with a processor typically include pre-applied thermal compound.

Over time, dust collects on the heat sink’s fins and the fan, which decreases its efficiency. Use compressed air or a PC vacuum to remove dust.

In some high-end gaming PCs, liquid cooling systems transfer heat from the CPU to a radiator using water and antifreeze. These work in much the same way as an automobile’s cooling system, providing excellent heat exchange and enabling much higher clock speeds than with air cooling.

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Figure 1-4 Manufacturer-supplied heat sinks for AMD (left) and Intel (right) CPUs.

System Memory

There are two major types of RAM (random access memory): dynamic and static. Dynamic RAM (DRAM) loses information in a very short period of time in the absence of power. Static RAM (SRAM) retains its data for longer periods without power and is faster than DRAM, but is bulkier and much more expensive. In general, DRAM is used as system memory, and SRAM is used for cache and storage devices.

Although the first PCs used individually socketed memory chips, memory modules (multiple memory chips on a small circuit board) were soon found to be more reliable and less bulky. Fast-page mode DRAM and Extended Data-Out (EDO) memory used a type of memory module called a single inline memory module (SIMM). The 30-pin SIMMs have 8-bit-wide memory access, and the 72-pin SIMMS have 32-bit-wide memory access.

Synchronous dynamic RAM (SDRAM) has replaced older forms of DRAM. Synchronous means that the data transfer is timed to the system clock. 168-pin SDRAM modules were the first type of SDRAM used in PCs. The next type of SDRAM was double data rate (DDR) memory in a 184-pin DIMM , and currently systems use DDR2 and DDR3 (both of which use 240-pin modules, but are not interchangeable). The memory modules used for SDRAM-class memory are known as dual inline memory module (DIMM). These modules provide 64-bit-wide memory access.

Like most things on a PC, RAM is measured in speed. The motherboard must support the speed of the RAM; otherwise, the increased performance promised by the fast RAM will not be realized, or worse, the PC might not even power-on self-test (POST).