One of the generic measures is MIPS (millions of instructions per second). This is only meaningful when comparing machines with the same architecture, since some architectures may require substantially more instructions than others for the same program. This method also can be very dependent on the mix of instructions and hence on the program used to measure MIPS. Some manufacturers report "peak MIPS" on carefully designed but useless programs.
It is obvious, that all major computer components such as CPU, memory and IO devices together affect computer's performance. Slow RAM or hard disk is going to be a bottleneck for fast CPU. In reality, however, high performance of PC is always a trade off to low cost:
Multiplex address/data Data bus width
Wider means faster
Low pin count is cheaper Bus masters
Multiple (requires arbitration)
Single (no arbitration) Transfer size
Let's take a look at the factors that influence computer performance in more detail:
CPU architecture is important. The higher the generation, the better. For example, because of high performance new features, Pentium 75 (fifth generation with the clock rate 75 MHz) outperforms 80486DX100 (which is the fourth generation CPU with the clock rate 100MHz). One of the techniques, enhancing the performance , is parallel processing. For example, while an instruction is being executed in the ALU (E), the next instruction can be fetched from memory (F) and decoded (D).
The drawing illustrates the idea of instruction-level parallelizm or pipelining.
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F1 F2 F3 F4
D1 D2 D3
Instruction Prefetching is another idea, first appeared in 286 (6...
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