Despite its elegance and flexibility, the concept of microprogramming did not take the industry by storm. The greatest criticism leveled against the idea was that it was inefficient. Wilkes’s approach was more complicated and circuitous than the usual way of building machines. There was also a performance disadvantage implied by the double decoding of instructions. Finally, fast memory, which was critical to implementation of the concept, was expensive. Thus many designers believed that they could build faster machines at lower cost by hardwiring the “right” set of instructions in the first place.
These criticisms were fair but missed the essential point. When Wilkes asserted that microprogramming was the “best way” to design a computer, he did not mean it was the “highest speed” or “lowest cost” approach. What Wilkes sought above all was flexibility and ease of improvement. More than anyone else of his generation, Wilkes expected all the components of the computer to get better over time.