Summary STUDY HARD

CS 405
COMPUTER SYSTEM ARCHITECTURE
MODULE-1 [PART-2]



System attributes to performance
¡ Performance demands a perfect match between

 machine capability

 program behaviour

¡ Machine capability

 Better hardware technology

 Innovative architectural features

 Efficient resources management

¡ Program behaviour

 Difficult to predict

 Algorithm design, data structure, compiler technology



Factors for projecting performance of a computer

¡ Simplest measure is turn around time, which includes

 Disk and memory access, Input and output activities

 Compilation time, OS overhead, CPU time




Performance factors


¡ Clock time(τ):

 Time need to complete one clock cycle

, ¡ Clock rate(f):

 Inverse of cycle time(f=1/ τ)

¡ Instruction count(Ic)

 No of machine instructions to be executed in the program

¡ CPI(cycles per instruction):

 Time need to execute each instruction.

¡ Processor cycle(p)

¡ Memory cycle(m)

¡ Ratio between memory and processor cycle(k)




CPU time
 Time needed to execute a program.
 Depends on following factors

Ic

CPI

Cycle Time



T=Ic*CPI*ꚍ


 It can be divided into 2 component terms
i. Processor cycle p
ii. Memory cycle m


Then the equation becomes:



T=Ic*(p+m*k)*ꚍ