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:
Registers - Registers are special storage locations located inside the CPU. The data contained here can be accessed much quicker than the data contained in other memory locations, such as the RAM (random-access memory) and the ROM (read-only memory). Registers in different parts of the CPU are used for different functions. In the control unit, the registers are used to store the computer's current instructions and the operands (this is merely a fancy term for data that is being operated on by the CPU). Meanwhile, the registers found in the ALU, called accumulators, are used to store the results of the arithmetic or logical operations.
Address Bus - The address bus is a collection of wires connecting the CPU with main memory that is used to identify particular locations (addresses) in main memory. The width of the address bus (that is, the number of wires) determines how many unique memory locations can be addressed.
Arithmetic/Logic Unit (ALU) - The ALU is the part of the CPU that does the actual computing and calculations sent to it by programs.
Cache
- Small memories on or close to the CPU chip can be made faster than the much larger main memory. Most CPUs since the 1980s have used one or more caches, and modern general-purpose CPUs inside personal computers may have as many as half a dozen, each specialized to a different part of the problem of executing programs. It is very similar to the concept of a browser cache that stores data from visited web sites making subsequent visits to those sites load faster.
Hyperthreading - The Intel Pentium 4 introduced hyperthreading which allows each pipeline to run more than one thread at a time. This essentially tricks the system into thinking that there are 2 processors. Hyperthreading only works with operating systems and applications that support it.
Chip Characteristics:
Note: You do not need to memorize the data in the following tables. It is here for reference purposes.
Processor
Speed (MHz)
Heat Sink
Cooling Fan
Cache
Package
Pins
8088
5-8
No
No
No
DIP
40
80286
6 10 12
No
No
No
LLC PGA PLCC
68
80386SX
16 - 33
No
No
No
PGA
100
80386DX
16 - 33
No
No
No
PGA
100
80486SX
16 - 33
No
Yes on 33 MHz
0-256K
PGA
100
80486DX
25 - 50
No
Yes on 33 MHz
0-256k
PGA SQFP
168 208
Pentium
60-166
Yes
Yes
256-512k
PGA
296
Pentium Pro
233-266
Yes
Yes
256k-1mb
PGA
387
Pentium II
233-500
Yes
Yes
512k
SEC
242
Pentium III
450mhz-1.13ghz
Yes
Yes
256-512k
SEC/PGA
242/370
Pentium IV
1.30-3.80ghz
Yes
Yes
256-512k
PGA
423/478/775
Itanium
733-833mhz
Yes
Yes
96k
PAC
418
Itanium II
900mhz-1.0ghz
Yes
Yes
256k
OLGA
611
Pentium D
2.6GHz-3.6GHz
Yes
Yes
2x1mb-2x2mb
OLGA
775
Intel Core
1.06GHz-2.33GHz
Yes
Yes
2mb
Micro FCPGA
478
Intel Core 2
1.8GHz-3.2GHz
Yes
Yes
2mb or 4mb
OLGA
775
With the Pentium MMX processors, 57 multimedia specific instructions were added to increase multimedia performance and increased the L1 cache size to 32KB.
The Pentium Pro added Dynamic Execution and increase L2 cache to 512KB.
The Pentium II had integrated MMX technology and used a new Single Edge Contact Cartridge(SEC).
The Pentium III provided increased processor speeds, a 100mhz front size bus speed and increased L2 cache to 512KB.
The Celeron processors are less expensive but only have a 66mhz bus and 128KB L2 cache.
The Pentium IV introduced a number of graphics enhancements. 2 versions were made - The first was a 423-pin PGA package with 256 KB L2 cache. The second version offers a 478-pin PGA package with 512 KB of L2 cache.
Intel Xeon processors are higher-end and based on their Pentium II, III and IV counterparts.
Bus Sizes of CPUs
Processor
Register
Data Bus
Address Bus
8088
16-bit
8-bit
20-bit
80286
16-bit
16-bit
24-bit
80386SX
32-bit
16-bit
24-bit
80386DX
32-bit
32-bit
32-bit
80486SX
32-bit
32-bit
32-bit
80486DX
32-bit
32-bit
32-bit
Pentium
64-bit
64-bit
32-bit
Pentium Pro
64-bit
64-bit
36 bit
Pentium II
64-bit
64-bit
36 bit
Pentium III
64-bit
64-bit
36 bit
Pentium IV
64-bit
64-bit
36 bit
Itanium
64-bit
64-bit
44 bit
Itanium II
64-bit
128-bit
44 bit
Pentium D
64-bit
???
???
Intel Core
???
???
???
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.
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.
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.
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.
