EEEE - 02-1 02-1 Components of CPU Performance and...

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Unformatted text preview: 02-1 02-1 Components of CPU Performance and Performance Equation Why is my computer fast (or slow)? Would it help to improve ? CPU performance equation is one way to start answering these questions. 02-1 EE 4720 Lecture Transparency. Formatted 9:21, 28 February 2011 from lsli02. 02-1 02-2 02-2 CPU Performance Decomposed into Three Components: Clock Frequency ( ) Determined by technology and influenced by organization. Clocks per Instruction (CPI) Determined by ISA, microarchitecture, compiler, and program. Instruction Count (IC) Determined by program, compiler, and ISA. These combined to form CPU Performance Equation t T = 1 CPI IC , where t T denotes the execution time. 02-2 EE 4720 Lecture Transparency. Formatted 9:21, 28 February 2011 from lsli02. 02-2 02-3 02-3 CPU Performance: Simple System Execution in program order . . . . . . one at a time. Instr. 1
 Instr. 2
 Instr. 3
 Time/cycles:
 Time/mms:
 0
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 Instr. 500,000
 1,999,996
 39,999,920
 IC = 500 , 000; = 50 kHz; CPI = 4. Execution time: IC CPI. clock period. Here ( and only here) CPI is number of cycles for each instruction. 02-3 EE 4720 Lecture Transparency. Formatted 9:21, 28 February 2011 from lsli02. 02-3 02-4 02-4 Execution: Pipelined, In Order To Run Faster: Overlap Instructions (Pipelined Execution) Result must be same as one-at-a-time execution . . . . . . not too difficult to achieve. Instr. 1
 Instr. 2
 Instr. 3
 Time/cycles:
 Time/mms:
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 Instr. 500,000
 750,000
 3,750,000
 Instr. 4
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 IC = 500 , 000; = 200 kHz; CPI = 750000 500000 = 1 . 5. Execution time at best: IC clock period . . . . . . assuming 1 cycle to start each instruction and . . . . . . instruction can start each cycle. (Slower in illustration.) 02-4 EE 4720 Lecture Transparency. Formatted 9:21, 28 February 2011 from lsli02. 02-4 02-5 02-5 Execution: Pipelined, Ideal Out of Order To Run Even Faster: Overlap Instructions and Start Out of Order Sometimes skip an instruction and execute it later. Instr. 1
 Instr. 2
 Instr. 3
 Time/cycles:
 Time/mms:
 0
 1
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 11
 0
 4
 8
 Instr. 500,000
 500,000
 500,000
 Instr. 4
 Instr. 5
 Instr. 6
 Instr. 7
 Instr. 8
 Instr. 9
 IC = 500 , 000; = 200 kHz; CPI = 1. Execution time at best: IC clock period . . ....
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This note was uploaded on 07/18/2011 for the course EE 4720 taught by Professor Staff during the Spring '08 term at LSU.

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EEEE - 02-1 02-1 Components of CPU Performance and...

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