Meaning
Internal memory within a processor holds the low-level instructions that define how complex machine code is executed by the underlying hardware. This storage area allows the chip designer to implement high-level instructions as sequences of simpler micro-operations. The microcode control store is typically faster than main memory and sits close to the execution units.
Instruction Translation
The decoders look up the micro-program associated with each incoming opcode. The instruction translation of the microcode control store converts a single cisc instruction into several risc-like steps. This mechanism allows the processor to handle complex operations without needing massive amounts of hard-wired logic.
Firmware Update
Modern processors allow for the modification of these internal instructions after the chip has been manufactured. The firmware update of the microcode control store provides a way to fix bugs or mitigate security vulnerabilities discovered in the silicon. These updates are loaded during the boot process and reside in volatile memory within the control store.
They must be re-applied every time the system starts.
Storage Capacity
Size limits on this internal memory restrict the number and complexity of instructions that can be supported. The storage capacity of the microcode control store is a primary factor in the design of the processor. Designers must balance flexibility with the area consumed on the die.
