Bài giảng Computer architecture: Part I

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Cùng tìm hiểu combinational Digital Circuits; Digital Circuits wit memory; computer System technology;... được trình bày cụ thể trong "Bài giảng Computer architecture: Part I - Background and Motivation".

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Nội dung Text: Bài giảng Computer architecture: Part I

Part I Background and Motivation Mar. 2006 Computer Architecture, Background and Motivation Slide 1
About This Presentation This presentation is intended to support the use of the textbook Computer Architecture: From Microprocessors to Supercomputers, Oxford University Press, 2005, ISBN 0-19-515455-X. It is updated regularly by the author as part of his teaching of the upper- division course ECE 154, Introduction to Computer Architecture, at the University of California, Santa Barbara. Instructors can use these slides freely in classroom teaching and for other educational purposes. Any other use is strictly prohibited. © Behrooz Parhami Edition Released Revised Revised Revised Revised First June 2003 July 2004 June 2005 Mar. 2006 Mar. 2006 Computer Architecture, Background and Motivation Slide 2
I Background and Motivation Provide motivation, paint the big picture, introduce tools: • Review components used in building digital circuits • Present an overview of computer technology • Understand the meaning of computer performance (or why a 2 GHz processor isn’t 2 as fast as a 1 GHz model) Topics in This Part Chapter 1 Combinational Digital Circuits Chapter 2 Digital Circuits with Memory Chapter 3 Computer System Technology Chapter 4 Computer Performance Mar. 2006 Computer Architecture, Background and Motivation Slide 3
1 Combinational Digital Circuits First of two chapters containing a review of digital design: • Combinational, or memoryless, circuits in Chapter 1 • Sequential circuits, with memory, in Chapter 2 Topics in This Chapter 1.1 Signals, Logic Operators, and Gates 1.2 Boolean Functions and Expressions 1.3 Designing Gate Networks 1.4 Useful Combinational Parts 1.5 Programmable Combinational Parts 1.6 Timing and Circuit Considerations Mar. 2006 Computer Architecture, Background and Motivation Slide 4
1.1 Signals, Logic Operators, and Gates Name NOT AND OR XOR Graphical symbol Operator x xy x y x y sign and _ alternate(s) x or x x y x y x y Output Both inputs At least one Inputs are Input is 0 is 1 iff: are 1s input is 1 not equal Arithmetic 1 x x y or xy x y xy x y 2xy expression Figure 1.1 Some basic elements of digital logic circuits, with operator signs used in this book highlighted. Mar. 2006 Computer Architecture, Background and Motivation Slide 5
Variations in Gate Symbols AND OR NAND NOR XNOR Figure 1.2 Gates with more than two inputs and/or with inverted signals at input or output. Mar. 2006 Computer Architecture, Background and Motivation Slide 6
Gates as Control Elements Enable/Pass signal Enable/Pass signal e e Data out Data in Data in Data out x or 0 x x x or “high impedance” (a) AND gate for controlled trans fer (b) Tristate buffer e e 0 0 0 No data 1 1 x ex x or x (c) Model for AND switch. (d) Model for tristate buffer. Figure 1.3 An AND gate and a tristate buffer act as controlled switches or valves. An inverting buffer is logically the same as a NOT gate. Mar. 2006 Computer Architecture, Background and Motivation Slide 7
Wired OR and Bus Connections ex ex x x ey ey Data out y (x, y, z, y Data out or high (x, y, z, or 0) impedance) ez ez z z (a) Wired OR of product terms (b) Wired OR of t ristate outputs Figure 1.4 Wired OR allows tying together of several controlled signals. Mar. 2006 Computer Architecture, Background and Motivation Slide 8
Control/Data Signals and Signal Bundles Enable Compl 8 / / / / / 8 / 32 / k 8 32 k (a) 8 NOR gates (b) 32 AND gat es (c) k XOR gat es Figure 1.5 Arrays of logic gates represented by a single gate symbol. Mar. 2006 Computer Architecture, Background and Motivation Slide 9
1.2 Boolean Functions and Expressions Ways of specifying a logic function Truth table: 2n row, “don’t-care” in input or output Logic expression: w (x y z), product-of-sums, sum-of-products, equivalent expressions Word statement: Alarm will sound if the door is opened while the security system is engaged, or when the smoke detector is triggered Logic circuit diagram: Synthesis vs analysis Mar. 2006 Computer Architecture, Background and Motivation Slide 10
Manipulating Logic Expressions Table 1.2 Laws (basic identities) of Boolean algebra. Name of law OR version AND version Identity x 0=x x1=x One/Zero x 1=1 x0=0 Idempotent x x= x xx=x Inverse x x =1 xx =0 Commutative x y=y x xy=yx Associative (x y) z = x (y z) (x y) z = x (y z) Distributive x (y z) = (x y) (x z) x (y z) = (x y) (x z) DeMorgan’s (x y) = x y (x y) = x y Mar. 2006 Computer Architecture, Background and Motivation Slide 11
Proving the Equivalence of Logic Expressions Example 1.1 Truth-table method: Exhaustive verification Arithmetic substitution x y = x + y xy x y = x + y 2xy Example: x y ? x y x y x + y – 2xy ? (1 – x)y + x(1 – y) – (1 – x)yx(1 – y) Case analysis: two cases, x = 0 or x = 1 Logic expression manipulation Mar. 2006 Computer Architecture, Background and Motivation Slide 12
1.3 Designing Gate Networks AND-OR, NAND-NAND, OR-AND, NOR-NOR Logic optimization: cost, speed, power dissipation (x y) = x y x x x y y y y y y z z z z z z x x x (a) A ND-OR circuit (b) Int ermediate circuit (c) NAND-NAND equivalent Figure 1.6 A two-level AND-OR circuit and two equivalent circuits. Mar. 2006 Computer Architecture, Background and Motivation Slide 13
BCD-to-Seven-Segment Decoder Example 1.2 e0 0 Signals to 4-bit input in [0, 9] enable or x3 x2 x1 x0 turn on the e5 5 1 segments e6 6 e4 4 2 e3 3 e2 e1 Figure 1.8 The logic circuit that generates the enable signal for the lowermost segment (number 3) in a seven-segment display unit. Mar. 2006 Computer Architecture, Background and Motivation Slide 14
1.4 Useful Combinational Parts High-level building blocks Much like prefab parts used in building a house Arithmetic components (adders, multipliers, ALUs) will be covered in Part III Here we cover three useful parts: multiplexers, decoders/demultiplexers, encoders Mar. 2006 Computer Architecture, Background and Motivation Slide 15
Multiplexers x0 0 x0 0 z x0 z z x1 x1 1 x1 1 y y y (a) 2-to-1 mux (b) Switch view (c) Mux symbol e (Enable) x0 0 x0 0 / x1 1 0 0 x1 1 z z 32 / y0 x2 2 / 1 32 x2 0 1 x3 3 32 y y1 x3 1 y1y0 y0 (d) Mux array (e) 4-to-1 mux with enable (e) 4-to-1 mux design Figure 1.9 Multiplexer (mux), or selector, allows one of several inputs to be selected and routed to output depending on the binary value of a set of selection or address signals provided to it. Mar. 2006 Computer Architecture, Background and Motivation Slide 16
Decoders/Demultiplexers y1 y0 y1y0 y1y0 x0 0 x0 0 x0 1 x1 x1 1 x1 e 2 x2 2 x2 (Enable) 3 x3 x2 3 x3 x3 (c) Demultiplexer, or (a) 2-to-4 decoder (b) Decoder symbol decoder wit h “enable” Figure 1.10 A decoder allows the selection of one of 2a options using an a-bit address as input. A demultiplexer (demux) is a decoder that only selects an output if its enable signal is asserted. Mar. 2006 Computer Architecture, Background and Motivation Slide 17
Encoders x0 x1 x0 0 x1 1 x2 x2 2 x3 3 x3 y1 y0 y1y0 (a) 4-to-2 encoder (b) Enc oder symbol Figure 1.11 A 2a-to-a encoder outputs an a-bit binary number equal to the index of the single 1 among its 2a inputs. Mar. 2006 Computer Architecture, Background and Motivation Slide 18
1.5 Programmable Combinational Parts A programmable combinational part can do the job of many gates or gate networks Programmed by cutting existing connections (fuses) or establishing new connections (antifuses) Programmable ROM (PROM) Programmable array logic (PAL) Programmable logic array (PLA) Mar. 2006 Computer Architecture, Background and Motivation Slide 19
PROMs Inputs w w x x . Decoder y y . . z z ... Outputs (a) Programmable (b) Logic equivalent (c) Programmable read-only OR gates of part a memory (PROM) Figure 1.12 Programmable connections and their use in a PROM. Mar. 2006 Computer Architecture, Background and Motivation Slide 20