Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Fourth Edition Microprocessors Chapter 6 © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Overview Fourth Edition • In this chapter, you will learn how to – Identify the core components of a CPU – Describe the relationship of CPUs and memory – Explain the varieties of modern CPUs – Select and install a CPU – Troubleshoot CPUs © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Fourth Edition Central Processing Unit (CPU) Core Components © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Concepts Fourth Edition • The CPU (central processing unit) works as a very powerful calculator. • CPUs are not very smart … just very fast at manipulating zeros and ones. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Man in the Box Fourth Edition • 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 you communicate with him? Figure 1: Imagine the CPU as a man in a box. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Man in the Box (continued) Fourth Edition Figure 2: How do we talk to the man in the box? © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Talking to the Man Fourth Edition • Imagine 16 lights – 8 on the inside and 8 on the outside – When an inside light is on, the corresponding outside light is on. You can switch these lights on and off – We call this communication system the external data bus Figure 3: Cutaway of the external data bus—note that one light bulb pair is on © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs External Data Bus Fourth Edition • The CPU communicates with the outside world using the external data bus (EDB) – Uses binary (1 is on, and 0 is off) to communicate – Data lines on the bus can be switched (turned on or off) from inside or outside. • There is a problem: The man in the box has no memory! He needs help to save information he's working on. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs External Data Bus (continued) Fourth Edition Figure 4: Close-up of the underside of a CPU © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Talking to the Man Fourth Edition • In reality, a lot of little wires flash on or off – Voltage is applied or not – Represented not as on, off, on, off… but as 1, 0, 1, 0… Figure 5: Here "1" means on, "0" means off. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Registers Fourth Edition • Inside the box are registers (worktables or temporary storage locations). • The four general-purpose registers found in all CPUs are AX, BX, CX, and DX. Figure 6: The four general-purpose registers © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Codebook Fourth Edition • The man in the box needs one more tool: the codebook or instruction set. – This codebook is called machine language. – One command is a line of code. – The complete set of commands for a processor is its instruction set. Figure 7: CPU codebook © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Codebook (Instruction Set) Fourth Edition • Here are some examples of real machine language for the Intel 8088: 10111010 The next line of code is a number. Put that number into the DX register. 01000001 Add 1 to the number already in the CX register. 00111100 Compare the value in the AX register with the next line of code. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs The CPU so Far Fourth Edition Figure 8: The CPU so far © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Clock Fourth Edition • 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. Figure 9: The CPU does nothing Figure 10: The CPU often needs more until activated by the clock. than one clock cycle to get a result. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Clock (continued) Fourth Edition • Clock speed is the CPU’s maximum speed, not the speed at which the CPU must run. – Used to synchronize eternal and external activity – One cycle per second = 1 hertz (Hz); 1 million cycles per second = 1 megahertz (MHz) – Every command requires at least two clock cycles. • Clock speed is the maximum clock cycles per second. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Clock (continued) Fourth Edition • A clock cycle is the time taken by the special wire to charge. – 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. • Clock Speeds – 1 hertz (1 Hz) = 1 cycle per second – 1 megahertz (1 MHz) = 1 million cycles per second – 1 gigahertz (1 GHz) = 1 billion cycles per second – Intel 8088 ran at 4.77 MHz – Modern CPUs run at 3+ GHz © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Clock Speeds Fourth Edition Figure 11: Where is the clock speed? © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs System Crystal Fourth Edition • System crystal governs CPU running speed • Modern motherboards use jumpers to select crystal speed Figure 12: One of many types of system crystals © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs System Crystal (continued) Fourth Edition • Crystal can clock a CPU with a rated speed higher than the crystal, but the CPU will operate at the slower speed of the crystal. – In other words, a 1 GHz crystal can clock a 2 GHz CPU, but the CPU will operate only as fast as the crystal clock—1 GHz. – Underclocking means running a CPU slower than its rated clock speed—it does not take advantage of all the power of the CPU. – Overclocking means to run a CPU faster than its maximum clock speed—it can fry the CPU. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Back to the External Data Bus Fourth Edition Figure 13: Diagram of an Intel 8088 showing the external data bus and clock wires © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Memory Fourth Edition • Memory is the computer's workspace. • Programs and data are stored on storage media (hard drives, etc.). • Media are not fast enough to provide data to CPU. • Memory takes programs and data and sends them to the CPU MUCH faster. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs RAM Fourth Edition • Random access memory (RAM) is organized like a spreadsheet, with each row holding eight bits (one byte). • Transfers and stores data to and from CPU in byte-sized chunks • Number of bytes of RAM varies from PC to PC, with today's PCs holding billions of bytes of RAM Figure 14: RAM as a spreadsheet © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs DRAM Fourth Edition • Computers use dynamic random access memory (DRAM) – Dynamic rather than static – Random rather than sequential – Circuits need power and to be refreshed to maintain data. Figure 15: Typical RAM © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Memory Controller Chip Fourth Edition • CPU and RAM need a method to communicate, so they use the EDB. • The CPU doesn't know how to talk to memory, so it needs a helper chip—the MCC. • The memory controller chip (MCC) is a device that facilitates the flow of data from the RAM to the CPU. Figure 16: Extending the EDB Figure 17: The MCC grabs a byte of RAM. © 2012 The McGraw-Hill Companies, Inc. All rights reserved Mike Meyers’ CompTIA A+® Guide to Managing and Troubleshooting PCs Address Bus Fourth Edition • 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 MCC which line of code it wants from RAM Figure 18: Address bus © 2012 The McGraw-Hill Companies, Inc.