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Microprocessors. Chapter 3. Overview. In this chapter, you will learn how to Identify the core components of a CPU Describe the relationship of CPUs and RAM Explain the varieties of modern CPUs Identify specialty CPUs Install and upgrade CPUs. Central Processing Unit (CPU) Core Components.
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Microprocessors Chapter 3
Overview • In this chapter, you will learn how to • Identify the core components of a CPU • Describe the relationship of CPUs and RAM • Explain the varieties of modern CPUs • Identify specialty CPUs • Install and upgrade CPUs
Concepts • The CPU (Central Processing Unit) works as a very powerful calculator • CPUs are not very smart…just very fast at manipulating zeroes and ones
Man in the Box • Visualize the CPU as a man in a box. • He will gladly perform anything you want him to do, but he can’t see or hear anything outside the box. • How can we communicate with him? Is anyone out there? We need some way to talk to the guy inside the box
Talking to the Man • Imagine 16 lights • 8 on the inside and 8 on the outside • When an inside light is on, the corresponding outside light is on. We can switch these lights on and off. • This communication system is like the external data bus
On On On On On Off Off Off 1 1 1 1 1 0 0 0 Talking to the Man • In reality, a lot of little wires flash on or off • Voltage is applied or not • Represented not as on, on, off, off…but as 1, 1, 0, 0…
External Data Bus • The CPU communicates with the outside world using the external data bus (EDB) • Instead of light bulbs, the EDB is made up of tiny wires • The state of a wire is expressed in a binary format, with zeroes and ones • Each discrete setting (series of zeroes and ones representing the state of the wires) of the EDB is a line of code in a program
Registers • Inside the box are registers (temporary storage locations) • The four general-purpose registers found in all CPUs are AX, BX, CX, and DX 10000101 11001001 00110101 10100001
Codebook • The man in the box needs one more tool: the codebook or instruction set • Called machine language • One command is a line of code • The complete set of commands for a processor is its instruction set
Clock • The CPU does no work until told to—even though data may be on the EDB • You need a buzzer to tell the man in the box to start • This is referred to as a clock • A clock is actually a stream of pulses zz 10000101 00110101 Time to work 10000101 00110101
Clock • A clock cycle is the time taken by the special wire to charge up • The CPU needs at least two clock cycles to act on each command • A cycle is one complete up and down segment of the sine wave • The maximum number of clock cycles that can be handled by the CPU is called the clock speed
System Crystal • The system crystal defines the speed at which the CPU and the rest of the PC operate • Quartz oscillator, usually soldered to the motherboard • Overheating results from overclocking the CPU (running it faster than its maximum clock speed)
10000101 11001001 00110101 10100001 In Summary • The CPU is like a man in a box • The external data bus gets data in and out of the CPU • Registers are used as temporary storage inside the CPU • The instruction set is like a codebook • The clock defines the speed of the CPU
Memory • Memory is a device that holds binary data • Memory was first stored on paper cards and then on magnetic cards and magnetic tapes • Problems • Serial access • Slow • Random access memory (RAM) to the rescue!
RAM • RAM is organized similar to a spreadsheet • Data can be read or written to by addressing the RAM location • Typically represented as KB, MB, GB, or TB • Volatile—zeroes outwhen power lost
MCC Memory Controller Chip • The memory controller chip (MCC) is a device that facilitates the flow of data from the RAM to the CPU
MCC Address Bus • The address bus enables the CPU to control the MCC • Another set of wires in addition to the external data bus • Used by the CPU to tell the Northbridge which line of code it wants from RAM
Address Bus • The number of wires in the address bus determines the maximum amount of RAM the CPU can handle • An 8088 had 20 wires, which provided 220 combinations (1,048,576 or 1 MB) • Many current CPUs use 36 wires, which provide 236 combinations (68,718,476,736 or 64 GB)
Terminology • Bits are represented as b (i.e., Kb) • Bytes are represented as B (i.e., KB)
Decimal Compared to Binary 643 Decimal 101 Binary 102 101 100 22 21 20 100 10 1 4 2 1 0 1 1 6 4 3 4 + 0 + 1 + 5 Decimal 600 + 40 + 3 643
Modern CPUs CompTIA A+Essentials
CPU Overview • Several specification are used to describe and compare CPUs: • Make (Intel, AMD) • Model (Pentium, Athlon, etc.) • Packages, or how it’s mounted (PGA, SEC, SEP) • External speed (speed of crystal) • Multiplier (applied to crystal) • Cache (L1 and L2) • Internal speed (speed when crystal multiplied) • Pipelining • Hyper-threading • We’ll cover these in older and newer CPUs
Manufacturers • Two main CPU makers • Intel • AMD • CPUs might look similar, but they are not interchangeable
Common CPU Packages • Pin grid array (PGA) • Most common • Number of pins vary by processor • Plugs into sockets that vary by processor • Single edge cartridge (SEC) • Single edge processor (SEP) is similar • Processor mounted on board • Board plugs into motherboard • Zero insertion force (ZIF) • Allows processor to be easily inserted • Arm locks processor in place
Pentium CPU—The Early Years • CPU makers have added a large number of improvements over the years • Larger external data buses • Larger address buses • Faster clock speeds • Intel introduced the Pentium CPU in the early 1990s • 32-bit registers • Speeds up to 300 MHz • Ability to run multiple programs at once • Access super-fast cache RAM • Processes two or more lines of code at the same time
32-bit Addressing • Current operating systems are referred to as 32-bit (232) • Can directly address 4 GB of memory • Early Pentiums had 32-bit address bus • Newer CPUs have 36-bit address bus • 236 allows addressing 64 GB of RAM • Some 32-bit operating systems address the extra memory via “extensions” • Memory is swapped in and out of the 4 GB base as needed
Pipelining • A pipeline is a series of steps taken by the CPU to process a command • Pipelining is the process of processing more than one command at a time through the use of separate sets of circuitry • Works like an assembly line • Commands go through the processor on a “conveyer belt” • Enables the processor to work on more than one thing at a time
1011 0101 1100 1010 1001 1111 1100 0111 1101 1101 0001 1101 1011 0110 1001 0001 Cache • Cache is separate storage area used for quick access of data • CPU runs faster than RAM • Using a faster RAM cache close to the CPU helps the CPU run without waiting • L1: close to the CPU and fastest • L2: faster than RAM RAM CPU RAM Cache
L2 Cache • L2 was originally on the motherboard • Referred to as external cache • Not uncommon on today’s CPUs • Size of the cache varies from 0 to 1 MB
Clock Speed and Multipliers • The clock is derived from the crystal • Referred to as external speed • Clock is multiplied and CPU runs at quicker speed • CPU runs at much quicker multiplied speed • 66 MHz crystal • Sent through a 2X multiplier • Gives a 132 MHZ CPU Original clock Clock with 2x multiplier Has twice as many cycles for CPU to operate with
CPU Voltages • Older CPUs needed 5 volts • CPU voltage was reduced to 3.3 volts • Later improvements reduced voltage even more with no single standard • Smaller size resulted in lower voltage and smaller chips • Voltage regulator module (VRM) is a small card that enables a CPU to standardize voltage regulators • CPU reports voltage requirements with CPUID
Improvements • Out-of-order processing • Enabled processors to predict data that was needed • 90% accuracy in pulling the correct data • On-chip L2 cache • On the same package, but not necessarily on the same chip
Bus Types • Frontside bus • Address bus and external data bus are combined together between the CPU, MCC, and RAM • Backside bus • Connection between the CPU and L2 cache • Remember that L2 cache used to be external cache but is now internal to the CPU housing CPU L2 Cache MCC RAM Backside bus Frontside bus
Pentium Improvements • MMX (multimedia extensions) • Designed for graphical applications • Increased clocks and multipliers • Up to 4.5x • Pentium II • Faster than Pentium Pro • Used SEC • AMD K6 • Proprietary 3DNow! • Requires a Super Socket 7
Older CPUs • Celeron • Offshoot of Pentium II for the low-end PC • Pentium III • Intel’s answer to 3DNow! by AMD • AMD Athlon • SEC package used slot A
IT Technician CompTIA A+Technician Processing and Wattage
Processing and Wattage • Wattage is a measure of power • Goal is to consume as little power as possiblewhile still having a powerful CPU • Solution: make it smaller so it takes less voltage;less voltage is less wattage • Processing • Measures thickness of wafers • Some of today’s processors are 65 nanometers • About as thick as 455 hydrogen atoms • Or 1/3077th of the width of a human hair Hydrogen atom
Pentium Competitors • AMD Athlon Thunderbird • Double-pumped frontside bus doubled the data rate without increasing the clock speed • Returned to PGA with Socket A • AMD Duron • Generic name given to all lower-end Athlon processors • AMD’s competitor to Intel’s Celeron for the low-end PC • Intel Pentium 4 (Willamette) • Completely redesigned core called NetBurst • Used 20-step pipeline • Quad-pumped frontside bus
Newer Processors • AMD Athlon XP (Palomino and Thoroughbred) • Enhanced version of the Athlon core processor • Intel Pentium 4 (Northwood, Prescott, Cedar Mill) • Increased frontside bus to 800 MHz • Introduced hyperthreading • Hyperthreading • Looks like two CPUsto the operating system