The Instruction Set Architecture (ISA) of a Central Processing Unit (CPU) refers to the lowest-level interface between the programmer and the CPU, and includes the following aspects:
- Data types
- Supported operand representations
- Operations on data
- Arithmetic/other operations that can be performed on the operands
- Instruction format
- Memory organization
- Addressing modes
ISAs are also often referred to as the "Programmers Model" of a CPU
PIC32MX, with the MIPS32® M4K® CPU core implements Release 2 of the MIPS32® architecture in a 5-stage pipeline. It includes the MIPS16e™ Application-Specific Extension (ASE), which improves code density through the use of 16-bit encodings of MIPS32 instructions plus some MIPS16e-specific instructions.
This ISA may be classified as a Load/Store or Register-Register type (i.e. ALU operations act on register operands only - no memory references). On modern CPUs, this is done to decouple CPU speed from main memory speed.