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 A+ Study Guide: Domain 1.0: Personal Computer Components: Processors

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Introduction:
The processor, also known as a microprocessor and the CPU, can be thought of as the brains of the system and is responsible for executing software commands and performing calculation functions. There are basically 2 CPU manufacturers today - Intel and AMD. Their processors are not interchangeable meaning that if you buy an AMD CPU, you must have a motherboard that supports AMD CPUs and vice versa.
 

Speed:
A CPU's capabilities are defined by their "instruction set" which are lines of code that are passed back and forth over the external data bus. CPUs are rated by clock speed - this is the speed is the maximum speed that the CPU can operate at. The motherboard has a system crystal soldered to it that sends a pulse out at a given speed that is received by the CPU. This is referred to as the system bus speed. The CPU will normally operate at the system bus speed even if it can handle faster speeds. With most CPUs it is possible to tell the clock chip to operate to multiply the system pulse to go faster than the CPU's designed speed. This is called overclocking which is a risky option that can lead to hardware failure.

Now all processors are capable of operating at much faster speeds than the chips on the motherboard. To deal with this, CPU manufacturers began creating clock-multiplying CPUs which can operate at faster speeds for internal functions (they still communicate at slower speeds over the address bus and external data bus). The external speed, also known as the front side bus or FSB, is multiplied by the multiplier to give the internal CPU speed. For example, if the FSB has a clock speed of 133 MHz and the CPU multiplier is 10x, then the processor would run at 1.33 GHz.

Voltage:
The transistors on a motherboard use 5 volts of electricity, however, CPUs have varying voltages. Decreasing the voltage allows manufacturers to use smaller transistors, and hence, fit more of them into the CPU. To deal with the varying voltages, modern motherboards have an integrated Voltage Regulator Module (VRM) that adjusts the voltage level that the CPU receives from the system.
 

CPU Terms:
 

Chip Characteristics:
Note: You do not need to memorize the data in the following tables. It is here for reference purposes.

Bus Sizes of CPUs
 

While Intel holds the majority of the processor market share, companies such as AMD have been producing clones based on the X86 architecture. The table below outlines the various socket/slot types and the processors that they support.
 

Current Trends:
A few years ago, Intel was the first to introduce a 64-bit processor (Itanium II). Since that time, 64 bit processors have become the standard. Clock speeds hit a brick wall at around 4GHz a few years back which forced CPU manufacturers to find new ways to squeeze more performance out of their chips. Intel and AMD both released "dual core" processors that are essentially 2 processors in one. The Intel Pentium D was basically 2 Pentium 4 processors together with their own cache. AMD launched a similar product called the AMD Athlon 64 X2 processor, however, the L1 cache was shared by the processors. Shortly after, Intel abandoned their Pentium line of processors which gave way to the Intel Core series. Core processors come in "Solo" or "Duo" (dual core) versions. This line was followed by the Intel Core 2 architecture that comes in "Duo" or "Extreme" versions.
 

Installing A Processor:
Before installing (or buying) a processor, you should make sure that your motherboard supports it. It is also very important to make sure that your motherboard uses the same package as your processor. In other words, a socket 775 processor (shown left) will not fit into a 478 socket. If you try to force it, you will likely bend the metal pins sticking out of the bottom of the processor. Typically, installation is as easy as placing the CPU in the socket and pushing down on the locking lever attached to the motherboard which can be seen on the left side of the image to the

left. This lever is located on the side of the socket. Most CPUs and sockets are keyed so that you place it in the correct spot.

Cooling:
CPUs get very hot and the faster the CPU, the hotter it will get. This is why we need to attach a fan or newer cooling method such as a liquid cooling system. A typical cooling fan is pictured to the right. Before you install your fan, place a little bit of thermal compound on the top of the CPU. The fan will typically have clamps that lock onto the side of the socket on the motherboard. These can be difficult to install. Be patient and try not to damage your motherboard, especially when removing the fan. After securing the fan, you will need to plug in the power cable to the appropriate spot on your motherboard. See your motherboard manual for the location.
 

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