Lec3-design - Outline of Today's Lecture An Overview of the...

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EEL-4713C Ann Gordon-Ross EEL-4713C Computer Architecture Introduction: the Logic Design Process EEL-4713C Ann Gordon-Ross Outline of Today’s Lecture ° An Overview of the Design Process Illustration using example of ALU design ° Reading: Appendix C.5-C6 EEL-4713C Ann Gordon-Ross The Design Process "To Design Is To Represent" Design activity yields description/representation of an object -- Distinguish concept from artifact -- The concept is captured in one or more representation languages -- This process IS design Design Begins With Requirements -- Functional Capabilities : what it will do -- Performance Characteristics : Speed, Power, Area, Cost, . . . EEL-4713C Ann Gordon-Ross Design Process Design Finishes As Assembly -- Design understood in terms of components and how they have been assembled -- Top Down decomposition of complex functions (behaviors) into more primitive functions -- Bottom-up composition of primitive building blocks into more complex assemblies CPU Datapath Control ALU Regs Shifter Nand Gate Design is a creative process, not a simple method
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EEL-4713C Ann Gordon-Ross Design as Search Design involves educated guesses and verification -- Given the goals, how should these be prioritized? -- Given alternative design pieces, which should be selected? -- Given design space of components & assemblies, which part will yield the best solution? Feasible (good) choices vs. Optimal choices Problem A Strategy 1 Strategy 2 SubProb 1 SubProb2 SubProb3 BB1 BB2 BB3 BB n EEL-4713C Ann Gordon-Ross Problem: Design a “fast” ALU for the MIPS ISA ° Requirements? ° Must support the Arithmetic / Logic operations ° Tradeoffs of cost and speed based on frequency of occurrence, hardware budget EEL-4713C Ann Gordon-Ross MIPS ALU requirements ° Add, AddU, Sub, SubU, AddI, AddIU => 2’s complement adder/sub with overflow detection ° And, Or, AndI, OrI, Xor, Xori, Nor => Logical AND, logical OR, XOR, nor ° SLTI, SLTIU (set less than) => 2’s complement adder with inverter, check sign bit of result EEL-4713C Ann Gordon-Ross MIPS arithmetic instruction format ° Signed arithmetic generates overflow, no carry R-type: I-Type: 31 25 20 15 5 0 op Rs Rt Rd funct op Rs Rt Immed 16 Type op funct ADDI 10 xx ADDIU 11 xx SLTI 12 xx SLTIU 13 xx ANDI 14 xx ORI 15 xx XORI 16 xx LUI 17 xx Type op funct ADD 00 40 ADDU 00 41 SUB 00 42 SUBU 00 43 AND 00 44 OR 00 45 XOR 00 46 NOR 00 47 Type op funct 00 50 00 51 SLT 00 52 SLTU 00 53
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EEL-4713C Ann Gordon-Ross Design Trick: divide & conquer ° Break the problem into simpler problems, solve them and glue together the solution ° Example: assume the immediates have been taken care of before the ALU 10 operations (4 bits) 00 add 01 addU 02 sub 03 subU 04 and 05 or 06 xor 07 nor 12 slt 13 sltU EEL-4713C Ann Gordon-Ross Refined Requirements
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This note was uploaded on 01/09/2012 for the course EEL 4713 taught by Professor Staff during the Spring '11 term at University of Florida.

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Lec3-design - Outline of Today's Lecture An Overview of the...

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