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1 CPU Study Guide As in most acronyms used in the world of computers, its definition is in its name. It is a centralized unit in the computer that does all the processing. Without the CPU, a computer would not be able to accomplish very much or get things done in a timely and orderly fashion. To better understand what a CPU is and how it works, I will use a simple analogy. Believe it or not, our human bodies also have a CPU, but it is called by a different name. It is the BRAIN. Our brain is the CENTRAL PROCESSING UNIT for all of the activity that happens in our bodies. 1. The CPU receives stimuli or input that is sent through the bus. (--- The brain receives its stimuli or input from the sense organs via the central nervous system.) 2. The CPU interprets their meaning or need. ( --- just as the brain does in the body.) 3. The CPU then responds by processing it. ( ---again, just like the brain does in the body.) Of course one is biological and continues to have many unexplored mysteries, and one is manmade. However, neither the body nor the computer would continue to work without its central processing unit or without something else helping to keep it running in the most primitive and basic sense. The path or roadway by which information flows to and from the brain is through the central nervous system, and in the computer, it is the BUS which accomplishes this. Description The CPU is the processor or central processor of the computer. It is a special silicon microprocessor chip that contains many internal circuits and components, including micro-sized transistors. Most of the calculations needed to perform tasks and operations on the computer happen in the CPU. As described above, the CPU is actually the most important component in the computer, for without it nothing of value could happen. It performs the arithmetic and logic operations needed to accomplish complicated tasks in the computer, and executes instructions to make things happen. The CPU is fed long streams of data via the system bus. The CPU receives at least two types of data: 1. Instructions on how to handle the other data. 2. Data, which must be handled according to the instructions. Which CPU? What determines which CPU is used inside a computer? All computers do not use the same CPU. It depends on the year the computer was made, and the design that the manufacturer put into the computer and its configuration. Different generations used different CPU's, and each succeeding generation came up with a newer and better CPU or central processor for making the computer run faster and more efficiently. Additionally, as competitors came into the market, each one worked at coming up with a unique and better solution in CPU design and function, working towards the goal of their CPU outperforming all others in the

2 market. The CPU is the brain of the computer. Sometimes referred to simply as the processor or central processor, the CPU is where most calculations take place. In terms of computing power, the CPU is the most important element of a computer system. What makes processors different from each other? There are three characteristics of a microprocessor that make them different from each other. A processor with a higher bit and MHz value is more powerful than one with lower values. A 32-bit microprocessor is more powerful than a 16-bit microprocessor, and a 100 MHz microprocessor is more powerful than a 50 MHz microprocessor. The following table describes the characteristics that determine and make microprocessors different from one another. Microprocessor Characteristics Instruction Set Bandwidth Clock Speed Microprocessor Characteristics Microprocessors execute individual sets of instructions, or basic programming commands to make things happen. Bandwidth is determined by the amount of bits or binary digits that are processed in a one individual instruction. The microprocessors speed. It is measured in MHz (megahertz - 1 MHz = 1,000,000 cycles per second.) The amount of instructions per second is determined by the clock speed, or how many individual instructions can be executed in one second of time. What does it look like? CPU's come in many different sizes and shapes and form factors, depending upon the generation it came from and its designer. Below are a 3 examples Click on the images for a larger view of the CPU example. AMD AMD Athlon Intel Celeron Components of a CPU & Criteria CPU Components

3 Microprocessor Arithmetic Logic Unit (ALU) Registers Control Unit RISC, CISC or VLIW Architecture? single integrated circuit. contains the circuit for both the arithmetic logic unit and the control unit. performs arithmetic and logic operations such as addition and subtraction. holds the data that is being processed. directs and coordinates processing. extracts instructions from memory. decodes and executes instructions. uses the ALU when needed. RISC = Reduced Instruction Set Computer - Recognizes a limited amount of instructions that can be executed. They also have less transistors and are therefore less expensive to make. This makes the instructions execute faster because the instructions are simplistic and uncomplicated. CISC = Complex Instruction Set Computer - Recognizes a greater amount of instructions that can be executed than RISC, which are more complex. This enables more complex operations to happen, and is therefore more intelligent. VLIW = Very Long Instruction Word - Capable of executing many operations within one clock cycle. Program instructions are reduced by a compiler, into basic operations that are performed at the same time instead of individually, by putting the operations into very long instruction words that are sent off to individual devices. CPU's & Killer Heat The CPU generates a lot of heat and is very sensitive to it. Older generation CPU's were not as fast as the ones we use today, and therefore did not create as much heat. The only cooling necessary to cool them was the air circulating in the computer case, from the power supply. With the ever-increasing speed and function ability of CPU's in the market today, heat has become a serious problem. To understand how the heat factor has changed from the original generations to today, try this simple exercise. 1. Hold both hands together, palm to palm. 2. Very slowly, rub them together back and forth. You may notice a little heat develop between your hands, but not much. 3. Now, start rubbing them together faster, increasing speed to as much as you possibly can. Notice that the heat builds up a lot more than before, and begins to feel uncomfortable. Now that you understand the basic heat factor involved in friction and movement, try to comprehend your hands moving thousands of times faster. The heat would become unbearable and would begin to break down the protective skin surface as well as begin to destroy everything under it. In the computer world, the increasing speeds of CPU's work in a similar way. The heat that builds up with faster speeds can begin a sort of meltdown, fusing circuits inside of it together, and therefore shorting it out. Heat Sinks

4 To prevent this meltdown from happening, we began by using a heat sink. A heat sink is made of aluminum or copper, which absorbs and dissipates heat more efficiently than other metals. It is designed with a flat base that is placed directly on and makes contact with the top of the CPU. Usually a thin film of a special heat sink paste (thermal grease) is applied between the CPU and the heat sink to aid in transferring the heat directly to the aluminum. The flat base is solid, but the rest of the heat sink is finned. The metal is designed to allow air to circulate in and around the fins to help with the heat dissipation. The heat sink is held in place by either 4 mounting screws, clips or clamps. They worked well, as long as they were routinely kept clean of dirt and dust that would find its way into the computer case and settle there. As in an earlier lesson on COMPUTER SAFETY, you learned that dirt and dust acts like a blanket, trapping heat underneath it. CPU Fan As CPU's continued to climb in speed, the heat sink by itself could no longer efficiently draw the deadly heat away from it. To alleviate this problem, a special fan was designed that drew very little current, and which would be efficient in helping to draw and blow heat away from the heat sink as it was absorbed. The fan and heat sink usually comes in a package deal, but can be purchased separately. The fan is secured to the heat sink, and the heat sink to the CPU. For a long time, this was all that was needed, and other than different designs, it did it's job well. Dust and dirt still would accumulate, and still would have to be routinely cleaned off of the unit. More Fans Needed Currently, as I write this study unit in the year 2002, CPU's are running at such high speeds, that a single fan and heat sink is not enough to keep everything at a safe temperature. In addition to the heat from the CPU, other processors are being used, such as those on video cards (some video cards now have their own fans). Removable or mobile hard drive bays are another example of how heat has continued to rise inside of the computer case (these also are beginning to incorporate their own fans.). To help overcome these added forms of heat building up, cases are now being designed with fan slots in strategic locations inside of the case. It is not uncommon to see at least 2 or more fans in addition to the CPU fan inside of a computer case. Some manufacturers also design additional vent ducting that is used for directing the heat directly outside of the case, rather than letting it circulate first. Additionally, many CPU and motherboard manufacturers have incorporated automatic operation and monitoring of fans through the use of onboard chips and or software. This software does more than monitor the temperature and speed of the fans, regulating them as needed. The software can also turn the computer off before damage can occur, and even alert you to the situation by telephoning or paging you. How is the CPU connected to the motherboard? The CPU is connected to the motherboard via a socket. The design and size of the socket has changed throughout the generations with the aim being towards ease of use. There have

5 basically been two types of sockets used. They are called the ZIF SOCKET (Zero Insertion Force) and the LIF SOCKET (Low Insertion Force). On the bottom of the CPU are many rows of pins, which can be easily damaged. LIF Socket (Low Insertion Force) The LIF socket type is basic, where the pins on the bottom of the CPU are pushed down into the corresponding pin holes in the LIF socket. Force is required to push the CPU in place, and you must be very careful not to bend the pins in the process. To remove the CPU, a special tool is required, which is simply called a chip removal tool. It is used to pry the CPU out of the socket. ZIF Socket (Zero Insertion Force) The ZIF socket alleviates the need to force the CPU into place. The CPU easily fits into the holes in the base of the ZIF socket and a lever is then used to hold the CPU securely in the slot. You are less likely to bend the pins and cause damage to the CPU with the ZIF socket types. Additionally, SLOTS have been used to house CPU's. Slot type CPU's are inserted into a slot that is similar to an adapter card slot. They are more expensive to produce, and therefore raise the price of the motherboard. Table of Socket Types The table below lists the various socket types, the CPU associated with it, amount of pins, and voltage used to power the CPU. SOCKET TYPE / NAME CPU PINS VOLTAGE SOCKET 1: 486 SX & DX 169 5v. SOCKET 2: 486 SX, DX, & DX v. SOCKET 3: 486 SX, DX, DX2, DX4, 586, Pentium Overdrive 237 3v. & 5v. SOCKET 4: Pentium 60 & v. SOCKET 5: Pentium 75, 90, v. SOCKET 6: 486 DX v. SOCKET 7: SUPER SOCKET 7: Intel Pentium & Pentium MMX, AMD K5/K6, Cyrix 686/686MX v & 3.3v. AMD K6-2, AMD K6-3, Cyrix 686-MII, Cyrix III v., 2.1v., 2.2v., 2.4v., 2.5v., 2.8v., 2.9v., 3.3v., 3.45v., 3.52v. SOCKET 8: Pentium Pro v. SOCKET 370: Intel Celeron, Pentium III SLOT I: Intel Pentium II, Pentium III SLOT II: Intel Pentium II Zeon, Pentium III Xeon SLOT A: AMD Athlon SOCKET A: AMD Athlon, AMD Duron

6 CPU History Since IBM (International Business Machines) was the first computer company, computers manufactured afterwards were called IBM Compatible. The vast majority of all CPUs mounted on PC motherboards from the early eighties are manufactured by Intel. Other companies that have tried competing include NEC, AMD (American Micro Devices), Texas Instruments, Cyrix, and Motorola, which makes the CPUs for Apple Computers. Below are charts of the CPU history, Intel Generations, Cyrix Generations, and AMD Generations. CPU HISTORY TABLE PC CPU Year Transistors FIRST SECOND THIRD FOURTH FIFTH FIFTH with Improvements SIXTH SIXTH with Improvements SEVENTH 8086 and , , DX and 80386SX , SX, 80486DX, 80486DX2 and 80486DX4 Pentium Cyrix 6X86 AMD K5 IDT WinChip C6 Pentium MMX IBM/Cyrix 6x86MX IDT WinChip2 3D Pentium Pro AMD K6 Pentium II AMD K6-2 Mobile Pentium II Mobile Celeron Pentium III AMD K6-3 Pentium III CuMine AMD original Athlon AMD Athlon Thunderbird Pentium ,200, ,100, ,500,000 4,500,000 6,000,000 6,000,000 5,500,000 8,800,000 7,500,000 9,300, ,400,000 18,900,000 9,300,000? 28,000, ,000,000 37,000,000 42,000,000 INTEL Processor History FIRST 8086 / 8088 S OF INTEL PC PROCESSORS 8-bit addressed 64K of RAM; 16-bit addressed 1 MB of RAM SECOND Protected Mode: addressed up to 16 MB RAM and could switch between multiple programs. Real Mode: running just DOS DX THIRD addressing bus and external data bus at 32 bits. Addressed up to 4 GIG of RAM.

7 386 Protected Mode: ability to open more than one program at a time. Had Virtual Memory (pretend RAM) in the hard drive called a swap file. Virtual 8086 to run DOS SX external data bus reduced to 16 bits. Address bus 24 bits. Addressed up to 4 GIG of RAM. 386 Protected Mode: ability to open more than one program at a time. Had Virtual Memory (pretend RAM) in the hard drive called a swap file. Virtual 8086 to run DOS. 486 (486 SX, 486 DX, 486 DX2, 486 DX4) 486 DX FOURTH Added 8 K level 1 on-board cache. Cache is memory stored for the CPU to use when the DRAM gets refreshed. DRAM has to be refreshed because the capacitors that are charging (1) or (0) discharging had down states. The Memory Controller then shuts down when the RAM gets refreshed. SRAM is faster and does not need to be refreshed by the capacitors. DX contains a math coprocessor for difficult math calculations over adding, multiplying, subtracting, and dividing. 1. PENTIUM - EARLY 1. Pentium P54C and P55C chip 64 bit external data bus bit internal bus MHz 4. First Pentiums were 5 Volts chip, large CPU chip 5. PGA 6. No multiplier k Level 1 cache - one for data, one for programs 2. PENTIUM - EARLY PART II FIFTH Same bus MHz 1. Multiplier not fixed, could be fractional X1, X1.5, X2.5, X3 2. A 75 MHz Pentium is really a 50Mhz Pentium X This is done by moving jumpers on the motherboard. External data bus speeds MHz 3.3 Volts Smaller CPU package - PGA Computer Names: Pentium, 586, 686 lines. 430LX (Mercury), 430NX (Neptune), 430 FX (Triton), 430HX (Triton II), 430VX (Triton II & III), 430TX

8 Pentium MMX series 1. PENTIUM PRO Intel 450GX/KX ("Orion"), Intel 440FX ("Natoma") Pentium Pro MMX series Same bus sizes as Pentium clock speeds Built in L2 cache - 256K, 512K. 1 MB Rectangular CPU shape for CPU and Level I & 2 cache Handled calculations with SPECULATIVE EXECUTION: CPU runs codes in cache while waiting for other codes. 2. LATER PENTIUM PROS MHz clock speeds (up to X5 clock multiplier) Split voltages 2.8 to 3.3 Volts Larger cache - 32K/32K 66 MHz MHZ internal bus speed Socket 7 MMX (Multimedia Extensions): support for high-end graphics SIXTH 3. PENTIUM II Intel 440LX (AGP port, DIMM - SDRAM) same bus as Pentium MHz clock speed (X3.5, X4, X4.5, X5 clock multiplier) 66 external bus speeds Pentium II (Deschutes - 333MHz) 100 MHz external bus speed X3.5, X 4 clock multipliers Built-in 2 512K caches CPU in SEC - Slot 1 CELERON 4. PENTIUM III SPEEDS: -33, -66, -100, -120, Pentium speeds are 75, 90, 100, 120, 133, 166, and 200, 233, 266. Pentium II speeds 233, 266, 300, and the new 333 MHz. SAMPLE READING OF A CHIP: 486DX4-100 printed on the chipset. SEVENTH PENTIUM 4 NetBurst Architecture

9 Increased Speed GHz on a 0.18 micron process with instructions being executed at a speed of 3 GHz Hyper-Pipelined Architecture - 20-stage pipeline design & Doubling of pipeline length Advanced Dynamic Execution & Rapid Execution Engine & New Improved X87 Floating Point 423-pin ZIF socket CYRIX Processor Table THIRD FOURTH FIFTH SIXTH OF CYRIX PROCESSORS had its 386 line had its 486 line 5X86 line, 6X86L (low voltage), 6X86 or M1, 6X86 PR200+ (bus speed 75 MHz), 6X86MMX line, etc. Cyrix M2 ACQUIRED BY VIA TECHNOLOGIES AMD Processor Table THIRD FOURTH FIFTH SIXTH had its 386 line had its 486 line, 5X86 AMD-K5 line, AMD-6 line AMD-K6-2 MMX, AMD-K6 3D MMX OF AMD PROCESSORS SEVENTH AMD K7 Athlon Voltage & Speed VOLTAGE: After the volt CPU was introduced, the voltage was reduced to 3.3 with the Pentium Processor. This reduced the amount of heat generated by the PC. Voltage was reduced further in later CPU's. SPEED: The CPU has a clock speed measured in Megahertz (MHz). The clock speed tells you how many operations the CPU will make in one second. (...quoted from PC Mechanic ) "Clock speed is basically how many times the CPU ticks per second. Every time it ticks (you don't hear the tick) an instruction gets performed. The clock speed is determined in Megahertz (MHz), which is a million cycles per second. Therefore, a 200MHz Pentium ticks 200 million times per second. Although clock speed isn't the only determining factor for performance and speed, it means an awful lot. The faster the clock speed, the faster the computer."

10 P-Rating System (...quoted from PC Mechanic) "Since Intel chips are the standard, it's chips are named by their clock speed. For example, the Pentium-200 is a Pentium chip that operates at 200 MHz. Intel's competitors use a P-RATING (PR) SYSTEM. The P-RATING system basically compares the chip with the equivalent Intel chip."...quoted from PC Mechanic MULTIMEDIA EXTENSION (MMX) Multimedia Extensions (MMX) Technology is a new breed of instruction built in to the newest Pentiums and virtually all later chips. MMX is an extension off the x86 instruction set that allows bytes of data, or instructions, to be packed together into a single register and operated on as one set of data, therefore reducing the amount of work that the chip has to do and allowing it to do more. MMX is thought to be mainly an improvement in multimedia performance, but this is not necessarily true. Its just that these types of applications stand to benefit most from this type of data handling. Such applications need to be specially designed to take advantage of MMX, and many vendors are releasing MMX enhanced software. How it Works: The following provided by Intel The Pentium processor with MMX technology has three primary architectural design enhancements. New Instructions : Intel engineers have added 57 powerful new instructions specifically designed to manipulate and process video, audio and graphical data efficiently. These instructions are oriented to the highly parallel, repetitive sequences often found in multimedia operations. SIMD Today's multimedia and communication applications often use repetitive loops that, while occupying 10 percent or less of the overall application code, can account for up to 90 percent of the execution time. A process called Single Instruction Multiple Data (SIMD) enables one instruction to perform the same function on multiple pieces of data. It allows the chip to reduce computer-intensive loops common with video, audio, graphics and animation. As an analogy, consider a drill sergeant telling an entire platoon, "About face," rather than commanding each individual soldier one at a time. More Cache Intel has doubled on-chip cache size to 32K on the Intel Pentium processor with MMX technology. Now, more instructions and data can be stored on the chip, reducing the number of times the processor has to access slower, off-chip memory areas for information."