At the hardware level, processors contain a number of separate areas of circuity, or "units", that perform … See more

Microcode was originally developed as a simpler method of developing the control logic for a computer. Initially, CPU instruction sets were hardwired. Each step needed to fetch, decode, and execute the machine in… See more

In 1947, the design of the MIT Whirlwind introduced the concept of a control store as a way to simplify computer design and move beyond ad hoc methods. The control store is a diode matrix: a two-dimensional lattice, whe… See more

• The Analytical engine envisioned by Charles Babbage uses pegs inserted into rotating drums to store its internal procedures.
• The EMIDEC 1100 reputedly uses a hard-wired control store consisting of wires threaded through ferr… See more

Each microinstruction in a microprogram provides the bits that control the functional elements that internally compose a CPU. The advantage over a hard-wired CPU is that internal CPU control becomes a specialize… See more

A few computers were built using writable microcode. In this design, rather than storing the microcode in ROM or hard-wired logic, the microcode is stored in a RAM called a writable control store or WCS. Such a co… See more

The design trend toward heavily microcoded processors with complex instructions began in the early 1960s and continued until roughly the mid-1980s. At that point the RISC design philosophy started bec… See more