Lec03c - COMP 4300 Computer Architecture Types of...

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1 COMP 4300 Computer Architecture Types of Instructions Dr. Xiao Qin Auburn University http://www.eng.auburn.edu/~xqin xqin@auburn.edu Fall, 2010
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2 Review: Types of Addressing Modes Addressing Mode Example Action 1. Register direct Add R4, R3 R4 <- R4 + R3 2. Immediate Add R4, #3 R4 <- R4 + 3 3. Displacement Add R4, 100(R1) R4 <- R4 + M[100 + R1] 4. Register indirect Add R4, (R1) R4 <- R4 + M[R1] 5. Indexed Add R4, (R1 + R2) R4 <- R4 + M[R1 + R2] 6. Direct Add R4, (1000) R4 <- R4 + M[1000] 7. Memory Indirect Add R4, @(R3) R4 <- R4 + M[M[R3]] 8. Autoincrement Add R4, (R2)+ R4 <- R4 + M[R2] R2 <- R2 + d 9. Autodecrement Add R4, (R2)- R4 <- R4 + M[R2] R2 <- R2 - d 10. Scaled Add R4, 100(R2)[R3] R4 <- R4 + M[100 + R2 + R3*d] Studies by [Clark and Emer] indicate that modes 1-4 account for 93% of all operands on the VAX.
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3 Generic Examples of Instruction Formats Variable: Fixed: Hybrid:
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4 Instruction Formats • If code size is most important, use variable length instructions: (1)Difficult control design to compute next address (2) complex operations, so use microprogramming (3) Slow due to several memory accesses If performance is most important, use fixed length instructions (1) Simple to decode, so use hardware (2) Works well with pipelining (3) Wastes code space because of simple operations Recent embedded machines (ARM, MIPS) added optional mode to execute subset of 16-bit wide instructions (Thumb, MIPS16); per procedure decide performance or density
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5 Types of Operations Arithmetic and Logic: AND, ADD Data Transfer: MOVE, LOAD, STORE Control BRANCH, JUMP, CALL System OS CALL, VM Floating Point ADDF, MULF, DIVF Decimal ADDD, CONVERT String MOVE, COMPARE Graphics (DE)COMPRESS
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6 80x86 Instruction Frequency Rank Instruction Frequency 1 load 22% 2 branch 20% 3 compare 16% 4 store 12% 5 add 8% 6 and 6% 7 sub 5% 8 register move 4% 9 call 1% 10 return 1% Total 96%
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7 Relative Frequency of Control Instructions Operation
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This note was uploaded on 12/07/2011 for the course COMP 3400 taught by Professor Staff during the Fall '10 term at Auburn University.

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Lec03c - COMP 4300 Computer Architecture Types of...

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