In the era of computer systems, time and performance is very important. To achieve that, computer scientists works hard to make CPUs better and faster. Most of the modern CPUs in present devices around the world make use of a performance feature called speculative execution. Speculative execution improves the performance of the CPU. It does that by guessing future tasks and executing the instruction. In normal cases, the task comes from the memory and it is executed by CPU, and results are stored in the storage. For better performance using speculative execution, the task is guessed by CPU and executed. When the task comes from memory, the CPU makes sure the correctness of its initial guess. If the guess was incorrect, the CPU reverts speculative execution. If the guess was correct, a significant performance gain is achieved.