Under normal real life scenarios, the CPU is frequently jammed waiting for other components to reply (mainly those like RAM and disk); and factors such as branches, registers and memory latencies tend to lower the IPC dramatically.
The IPC or (inter-process communication) depends on the computer core architecture and the amount of work burden.
However, under the ideal circumstances mentioned above (like nothing breaking the sequential flow) the microprocessor can execute over 100 billion instructions per second.