Page "Microcode" Paragraph 19

From the 1940s to the late 1970s, much programming was done in assembly language ; higher level instructions meant greater programmer productivity, so an important advantage of microcode was the relative ease by which powerful machine instructions could be defined.

During the 1970s, CPU speeds grew more quickly than memory speeds and numerous techniques such as memory block transfer, memory pre-fetch and multi-level caches were used to alleviate this.

High level machine instructions, made possible by microcode, helped further, as fewer more complex machine instructions require less memory bandwidth.

For example, an operation on a character string could be done as a single machine instruction, thus avoiding multiple instruction fetches.