Characteristics of risc processor

RISC ARCHITECTURE CHARACTERISTICS

Simple Instructions are used in RISC architecture. RISC helps and supports few simple data types and synthesize complex data types. RISC utilizes simple addressing modes and fixed length instructions for pipelining. In RISC, more RAM is required to store assembly level instructions.

Main Characteristics of RISC Architectures:

The instruction set is limited and includes only simple instructions. Only LOAD and STORE instructions reference data in memory. Instructions use only few addressing modes. Instructions are of fixed length and uniform format.

RISC, in full Reduced Instruction Set Computer, information processing using any of a family of microprocessors that are designed to execute computing tasks with the simplest instructions in the shortest amount of time possible. RISC is the opposite of CISC (Complex Instruction Set Computer).

Advantages of RISC processors

Due to the architecture having a set of instructions, this allows high level language compilers to produce more efficient code. This RISC architecture allows simplicity, which therefore means that it allows developers the freedom to utilise the space on the microprocessor.

Typical distinguishing characteristics of RISC organization are, Fewer number of instructions with fixed format. With reduced instruction set pipelining technique can be applied effectively. RISC processors response for interrupts are more effective compared to CISC.

RISC (Reduced Instruction Set Computer)

RISC-based machines execute one instruction per clock cycle. CISC machines can have special instructions as well as instructions that take more than one cycle to execute. The CISC architecture can execute one, albeit more complex instruction, that does the same operations, all at once, directly upon memory.

In common CISC chips are relatively slow (compared to RISC chips) per instruction, but use little (less than RISC) instructions. Therefore fewer, simpler and faster instructions would be better, than the large, complex and slower CISC instructions. However, more instructions are needed to accomplish a task.

The performance of RISC processors is often two to four times than that of CISC processors because of simplified instruction set. This architecture uses less chip space due to reduced instruction set. RISC processors can be designed more quickly than CISC processors due to its simple architecture.

So we can say our processor 8085 is a RISC and controller 8051 is a CISC. Reduced instruction set Computer. It is a type of microprocessor that has been designed to carry out few instructions at the same time.

An ARM processor is one of a family of CPUs based on the RISC (reduced instruction set computer) architecture developed by Advanced RISC Machines (ARM). ARM makes 32-bit and 64-bit RISC multi-core processors.

The 8086-based processors are an example of a complex instruction set computer, or CISC, architecture. Many newer processor designs use a reduced instruction set computer, or RISC, architecture instead.

For instance, the Microchip Technology PIC has been labeled RISC in some circles and CISC in others. The 6502 and 6809 have both been described as RISC-like, although they have complex addressing modes as well as arithmetic instructions that operate on memory, contrary to the RISC principles.

– PIC microcontroller use RISC because there is a perception that RISC is faster than CISC: – Ex: A processor with MUL and other one with only ADD. A processor with (ADD X(i),B,C) and other (ADD,Store).

When pipelining is done with a CISC processor it is done at a different level. The execution of instructions is broken down into smaller parts which can then be pipelined. In effect, The CISC instructions are translated into a sequence of internal RISC instructions, which are then pipelined.