Performance and CPU Comparisons

SPEC Power Benchmark

As performance increases so does power consumption. Even at 0 performance, 80 watts are used

Clock cycles per instruction(CPI)

Average number of clock cycles per instruction for a program or program fragment. Clock Cycles= Instruction Count x Cycles per instruction CPU Time= Instruction Count x CPI, Clock Cycle Time CPU Time= (Instruction Count x CPI)/ Clock Rate

Relative Performance

Execution time(b)/Execution time(b) = n

ARMv7 is much closer to MIPS than ARMv8 since ARMv7 and MIPS came out at the same time.

False

CPU time depends on 3 factors: how many high-level language instructions an average CPI (clock cycles per instruction) the clock cycle time

False

The ARM corporation is a leading chip manufacturer.

False

The authors of our textbooks recommend using the MIPS (millions of instructions / second) metric for evaluating CPUs.

False

CPU time depends on 3 factors: how many machine language instructions an average CPI (clock cycles per instruction) the clock cycle time

True

Performance

1/Execution time

Instruction mix

A measure of the dynamic frequency of instructions across one or more programs

millions instruction per second(MIPS)

A measurement of program execution speed based on the number of millions of instructions. MIPS is computed as the instruction count divided by the product of the execution time and 10^6

Benchmark

A program selected for use in comparing computer performance.

General-purpose Register(GPR)

A register that can be used for addresses for data with virtually any instruction

Amdahl's Law

A rule stating that the performance enhancement possible with a given improvement is limited by the amount that the improved feature is used. It is a quantitative version of the law of diminishing returns T(improved)= (T(affected)/ improvement factor)+T(unaffected) T(unaffected) = (100-T(affected))

Workload

A set of programs run on a computer that is either the actual collection of applications run by a user or constructed from real programs to approximate such a mix. A typical workload specifies both the programs and the relative frequencies.

CPU Execution Time

Also called CPU time. The actual time the CPU spends computing for a specific task.

Throughput

Also called bandwidth. Another measure of performance, it is the number of tasks completed per unit time.

Response Time

Also called execution time, The total times required for the computer to complete a task, including disk accesses, memory accesses, I/O activities, operating system overhead, CPU execution time, and so on.

Clock Cycle

Also called tick, clock tick, clock period, clock, or cycle. The time for one clock period, usually of the processor clock, which runs at a constant rate

CPU Execution TIme for a Program

CPU clock cycles for a program x Clock cycle time, or CPU clock cycles for a program/ clock rate

ARMv8 is a 32-bit processor.

False(64 bit)

The x86 is a RISC architecture.

False(It's ARM and MIPS)

A CPU operating at 4 GHz has 4 clock cycles every nanosecond.

False(if it was Hz not GHz)

The fact that CPU manufacturers could not increasing the clock rate of uniprocessors, led to the development of: _________ __________ chips.

Multicore

Performance Ratio

Performance(A)/ Performance(B)

In the mid-2000s, CPU developers found it difficult to increase the clock rate of uniprocessors due to the

Power Wall

User CPU time

The CPU time spent in a program itself

System CPU Time

The CPU time spent in the operating system performing tasks on behalf of the program.

Clock Period

The length of each clock cycle

Instruction Count

The number of instructions executed by the program

ARMv8

● 2007 design began; released 2013 ● much closer to MIPS than ARMv7 because: ○ got rid of the 4-bit conditional execution field ○ has 32 general-purpose registers ○ includes a divide instruction

x86

● MIPS and ARM were developed by small groups, starting in 1985 ● x86 is the product of many groups over decades (look at evolution)

ARMv7

● chips used in phones, tablets ● ARM licenses their IP (intellectual property) to manufacturers ● ARM is a RISC architecture like MIPS ● MIPS has more registers ● ARM has more addressing modes and instruction formats