Hello, everyone! I’ve been doing some research into computer hardware lately, and one thing that I keep coming across is this idea that the speed of a processor, while important, isn’t the only thing that affects a computer’s overall performance. I’m having a bit of a hard time wrapping my head around this because I always thought that a faster processor meant a faster computer. Can anyone explain why this isn’t necessarily the case? I’m really interested to learn more about this!
In: 97
A theoretical simple CPU will execute once instruction every clock cycle, so in that case, more cycles per second = more instructions per second. In reality, most instructions take more than one cycle to execute, simple instructions might take one or a few cycles per instruction while complex instructions might take a couple of dozen of cycles. These instructions take more CPU cycles but they also perform more sophisticated operations that would have taken more CPU cycles with a simpler set of instructions.
Modern CPUs also employ a technique call pipelining which will allows a CPU to start the execution of the next instruction in the next clock cycle, while the previous instruction is still executing. Obviously, if the next instruction depends on data that would be computed by the previous instruction, it has to wait for the result. To mitigate this issue, CPU designers came up with another technique called speculative execution which would try to “guess” the result of unfinished instructions and continue execution. These techniques improve performance but they seriously muddy the relationship between clock cycles and performance. At any given clock cycle, the CPU is executing a range of instructions because of the pipeline and some of that computation gets discarded because the CPU didn’t make the right guess on a speculative execution.
Latest Answers