ARCHITECTURAL COMPONENTS

Transcription

1 ARCHITECTURAL COMPONENTS Reading: Chapter 4 (sections ) ISE218 Fundamentals of Information Technology 2 Objectives Learn the common computer components Understand how each component contributes to program execution 1

2 3 CPU Programs and data are both stored in memory The computer s Central Processing Unit (CPU) fetches, decodes, and executes program instructions The principal parts of most CPUs are Arithmetic logic unit (ALU) Registers Control unit Internal bus 4 ALU Performs operations Addition Multiplication Comparison The control unit tells the ALU which operations to perform Operations synchronized by the clock 2

3 5 Registers Very fast memory Located very close to the ALU Processors vary in Number of registers Type of registers (e.g., address, integer, floating point, general purpose) Bits in each register Example register used to hold an instruction loaded from memory 6 Control Unit The control unit Monitors the execution of instructions Coordinates traffic to and from the CPU Decodes instructions Controls the ALU Includes a program counter 3

4 7 Internal Computer Bus Allows CPU components to communicate 8 CPU Basics Registers hold data that can be readily accessed by the CPU The arithmetic-logic unit (ALU) carries out logical and arithmetic operations as directed by the control unit The control unit determines which actions to carry out according to the values in a program counter register and a status register e.g., ALU does 2 s complement addition 4

5 9 Printed Circuit Board (PCB) Keeps computer system components in place electrically connects electronic components Contains conductive tracks More reliable than wiring components 10 Motherboard The central printed circuit board (PCB) in many modern computers Holds many of the crucial components of the system provides connectors for other peripherals. Alternatively known as the mainboard, system board, or, on Apple computers, the logic board 5

6 11 Motherboard Components* Sockets (or slots) in which one or more microprocessors may be installed Slots into which the system's main memory is installed A chipset - forms an interface between the CPU's front-side bus, main memory, and peripheral buses Non-volatile memory chips (firmware or BIOS) Clock generator Slots for expansion cards (these interface to the system via the buses supported by the chipset) Power connectors * From Wikipedia Relates mainly to desktops and servers Recent motherboards include integrated controllers (e.g., sound, graphics, network) 12 CPU Socket Allows the CPU to be replaced without soldering Functions: a physical structure to support the CPU support for a heat sink forms an electrical interface both with the CPU and the PCB Also referred to as a slot 6

7 13 Connectors Transmit information from one part of a computer to another 14 The Bus The bus connecting the CPU and memory is called the system bus The system shares data with other system components by way of a data bus PCI bus slots provide attachment for expansion cards Increasingly integrated into motherboards or by USB devices 7

8 15 Bus Details A set of connections that connect multiple subsystems within a computer Usually connects multiple components Connections for addresses, data, and control Uses a bus protocol Bus protocol is the set of rules for moving data between devices In a computer with 2 n memory addresses, how wide is the address bus? 16 Clocks Every computer contains at least one clock that synchronizes the activities of its components A fixed number of clock cycles are required to carry out each data movement or computational operation The clock frequency, measured in megahertz or gigahertz, determines the speed with which operations are carried out Clock cycle time is the reciprocal of clock frequency An 800 MHz clock has a cycle time of 1.25 ns 8

9 17 Clocks Clock speed is related to CPU performance but not an exact relationship Improve CPU performance throughput by reducing the number of instructions in a program, the number of cycles per instruction, or the number of nanoseconds per clock cycle Other superscalar approaches are possible 18 Are We on Track? What is the approximate instruction rate of the Apple iphone 6 processor (Apple A9) in GHz? And how many processors? 2 processors, 1.85 GHz What is the approximate instruction rate of the Samsung Galaxy S5? And how many processors? 4 processors at 2.1 GHz and 4 processors at 1.5 Ghz Most people refer to the processor rate on a multi-core processor as the per-processor rate 9

10 19 Are We on Track? Is a 1GHz dual core processor as powerful as a 2GHz single core processor? 20 Memory Notation L x W (length x width) Example 4K x 8 Memory has 4K (2 12 ) addressable locations Each addressable location is 8 bits wide (byte addressable) Address Data Each byte is addressable 10

11 21 Memory Organization Computer memory consists of a linear array of addressable storage cells Memory can be byte-addressable, or wordaddressable, where a word typically consists of two or more bytes If the memory word size of the machine is 16 bits, then a 4M 16 RAM chip gives us 4M of 16-bit memory locations 22 Addressing Memory 4M can be expressed as 2 12 (4,096) 2 10 (1,024) = 2 22 addressable words The memory locations for this memory are numbered 0 through Thus, the memory bus of this system requires at least 22 address lines The address lines count from 0 to in binary Each line is either on or off (1 or 0), indicating the address of the desired memory element 11

12 23 Address Lines Addresses and data are usually transmitted in parallel 24 Memory Addressing Example If memory contains: Memory Size Memory Address Size Addresses 2 bytes 0 and 1 1 bit 4 bytes 00, 01, 10, 11 2 bits 8 bytes 000, 001, 010, 011, 100, 101, 110, bits 2 n 00000, 00001, n bits e.g., n=5 12

13 25 Memory Organization Physical memory usually consists of more than one RAM chip Access is more efficient when memory is organized into banks of chips with the addresses interleaved across the chips Low-order interleaving - low order bits of the address specify which memory bank contains the address of interest High-order interleaving - high order address bits specify the memory bank Are We On Track? How many bits are required to address an 8G x 16 main memory if Main memory is byte-addressable? Main memory is word-addressable? 13

14 27 Were We on Track? How many bits are required to address an 8G x 16 main memory if Main memory is byte-addressable? Main memory is word-addressable? Memory contains 16GB If each byte is addressable, there are 16G addresses or 2 4 * 2 30 = 2 34 addresses, which requires 34 bits If each word is addressable, we only need 33 bits for the address 28 Interrupts The normal execution of a program is altered when an event of higher-priority occurs CPU is alerted to an event through an interrupt Interrupts can be triggered by I/O requests, arithmetic errors (such as division by zero), or when an invalid instruction is encountered Each interrupt is associated with a procedure that directs the actions of the CPU when an interrupt occurs Non-maskable interrupts are high-priority interrupts that cannot be ignored. 14

15 29 The Input/Output Subsystem A computer communicates with the outside world through its input/output (I/O) subsystem I/O devices connect to the CPU through various interfaces I/O can be memory-mapped-- where the I/O device behaves like main memory from the CPU s point of view Or I/O can be instruction-based, where the CPU has a specialized I/O instruction set 30 Did You Satisfy the Objectives? Learn the common computer components Understand how each component contributes to program execution 15