An Instruction Set Architecture (ISA) defines the communication rules between the hardware and software of the computer. The ISA is a design principle (conceptual) and not stored in a computer’s memory.
Some things an ISA defines:- How binary instructions are formatted- What instructions are available to beprocessed on a specific hardware setup- How computer memory, (volatile andnon-volatile) is accessed
CISC (Complex Instruction Set Computer) is an ISA design practice that focuses on multi-step instructions and complex, power-consuming hardware. These designs primarily focus on hardware components and binary instruction complexity. Processing components are typically not interchangeable with RISC-designed systems.
CISC Instructions Attributes:- Single instructions take more than one CPUcycle to complete- Instruction length varies based on theinstruction type- Hardware must be designed to accept morecomplicated instructions
RISC (Reduced Instruction Set Computer) is an ISA design practice of ISAs that focuses on simple, quickly executed instructions to improve efficiency and reduce power consumption. These designs primarily focus on simple hardware components and reducing binary instruction complexity. Processing components are typically not interchangeable with CISC-designed systems.
General RISC Instructions Attributes:- Single instructions take only one CPUcycle to complete- Instruction lengths are fixed, regardlessof the instruction type- Reduced complexity of hardware leads to lesspower consumption at the expense of overallprocessing times.
The Control Unit (CU) on a CPU receives information from the software; then, it distributes and directs the data to the relevant hardware components.
Some functions of the CU:- Determine what/where the nextinstruction must go for processing- Send clock signals to all hardware toforce synchronous operations- Send memory taskings if appropriate
An Arithmetic Logic Unit (ALU) is a digital circuit used to perform arithmetic and logic operations. It is the fundamental building block of the CPU.
Some ALU functions:- Addition & subtraction- Determining equality- AND/OR/XOR/NOR/NOT/NAND logicgates and more!
Computer instructions are written in binary, also known as machine code. Computer hardware operates on a series of these binary instructions through pulsating power signals that signify either
ON based on the binary digits
A register is a volatile memory system that provides the CPU with rapid access to information it is immediately using.
Functions of a register:- Store temporary data for immediateprocessing by the ALU- Hold "flag" information if an operationresults in overflow or triggers other flags- Hold the location of the next instructionto be processed by the CPU