What is a question about this article? If the question is unanswerable, say "unanswerable".

The control unit, ALU, and registers are collectively known as a central processing unit (CPU). Early CPUs were composed of many separate components but since the mid-1970s CPUs have typically been constructed on a single integrated circuit called a microprocessor.

Since when have CPUs been constructed with a microprocessor?
mid-1970s