pipe2 - Data Hazards ADD SUB AND OR XOR R1, R2, R3 R4, R5,...

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ipeline Hazards Pipeline Hazards or Danger!Danger!Danger! CSE 240A Dean Tullsen Data Hazards ADD R1, R2, R3 SUB R4, R5, R1 AND R6, R1, R7 R R8 1 R9 OR R8, R1, R9 XOR R10, R1, R11 Data ___________ may result in data ____________. CSE 240A Dean Tullsen Data Hazards add R1, R2, R3 sub R4, R1, R6 d R6 R1 R2 and R6, R1, R2 or R8, R11, R1 xor R10, R1, R5 CSE 240A Dean Tullsen Data Hazard add R6, R2, R1 addi R3, R1, #35 lw R8, 10000(R3) CSE 240A Dean Tullsen
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Data Dependence Data hazards are caused by data dependences Data dependences, and thus data hazards, come in 3 flavors (not all of which apply to this ipeline). pipeline). (read-after-write) (write-after-write) (write-after-read) CSE 240A Dean Tullsen RAW Hazard later instruction tries to read an operand before earlier instruction rites it writes it The dependence add R1, R2, R3 sub R5, R1, R4 The hazard add R1, R2, R3 sub R5, R1, R4 IF ID EX MEM WB IF ID EX MEM WB RAW hazard is extremely common CSE 240A Dean Tullsen WAW Hazard later instruction tries to write an operand before earlier struction writes it instruction writes it The dependence add R1, R2, R3 sub R1, R2, R4 The hazard 1 2 R3 lw R1, R2, R3 sub R1, R2, R4 AW hazard possible in a reasonable pipeline, but not IF ID EX MEM WB IF ID EX MEM WB MEM3 MEM2 WAW hazard possible in a reasonable pipeline, but not in the very simple pipeline we’re assuming. CSE 240A Dean Tullsen WAR Hazard later instruction tries to write an operand before earlier instruction ads it reads it The dependence add R1, R2, R3 sub R2, R5, R4 The hazard? add R1, R2, R3 sub R2, R5, R4 AR hazard is uncommon/impossible in a reasonable (in rder) IF ID EX MEM WB IF ID EX MEM WB WAR hazard is uncommon/impossible in a reasonable (in-order) pipeline CSE 240A Dean Tullsen
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This note was uploaded on 01/21/2010 for the course CSE240A 662015 taught by Professor Tullsen,deanmichael during the Fall '09 term at UCSD.

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pipe2 - Data Hazards ADD SUB AND OR XOR R1, R2, R3 R4, R5,...

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