12 02 19

Pagina 1

Surname (Cognome) SOLUTION Name (Nome) POLIMI ID Number Signature (Firma) Politecnico di Milano, February 12, 2019 Course on Advanced Computer Architectures Prof. D. Sciuto, Prof. C. Silvano EX1 ( 5 points) EX2 ( 5 points) EX3 ( 6 points) Q1 ( 5 points) Q2 ( 5 points) SIX QUESTIONS ( 6 points) TOTAL (32 points) Course on Advanced Computer Architectures EXAM 12/02/2019 – Please write by PEN in CAPITAL LETTERS & BLACK/BLUE!!! Page 1 - SOLUTION EXERCISE 1 – SCOREBOARD (5 points) Please consider the program in the table be executed on a CPU with dynamic scheduling based on SCOREBOARD BASIC SCHEME with:  2 LOAD/STORE units (LDU1, LDU2) with latency 4 cycles  1 FP UNIT (FPU1) with latency 3 cycles  1 ALU/BR UNIT (ALU1) with latency 1 cycle 1. Please complete the SCOREBOARD TABLE by assuming all cache HITS ISTRUZIONE ISSUE READ OPS EXEC COMPL WRITE BACK Hazards Type UNIT I0 lw $f5,0($r1) 1 2 6 7 LDU1 I1 lw $f6,0($r1) 2 3 7 8 LDU2 I2 fadd $f6,$f6,$f5 9 10 13 14 WAW $f6 I1 in ISSUE (RAW $f6 & RAW $f5 OK) FPU1 I3 sw $f6,0($r1) 10 15 19 20 RAW $f6 LDU1 I4 lw $f6,4($r1) 15 16 20 21 WAW $f6 I2 in ISSUE (WAR $f6 I3 in WB ok) LDU2 I5 fadd $f6,$f6,$f6 22 23 26 27 WAW $f6 I4 in ISSUE (RAW $f6 OK) FPU1 I6 sw $f6,4($r1) 23 28 32 33 RAW $f6 LDU1 I7 addi $r1,$r1,8 24 25 26 29 WAR $r1 I6 in WB ALU1 2. Express the formula then compute the following metrics:  CPI = (#clock cyles / IC) = 33/8 = 4.125  IPC = 1/CPI = 0.24 Course on Advanced Computer Architectures EXAM 12/02/2019 – Please write by PEN in CAPITAL LETTERS & BLACK/BLUE!!! Page 2 - SOLUTION EXERCISE 2 – SCOREBOARD (5 points) Please consider the previous exercise with the introduction of the following OPTIMIZATIONS:  CHECK FOR WAW postponed to WRITE BACK phase  FORWARDING PATHS 1. Please complete the SCOREBOARD TABLE by…