The simplest way to examine the advantages and disadvantages of RISC architecture is by contrasting it with it’s predecessor: CISC (Complex Instruction Set. RISC and CISC Architectures – Difference, Advantages and . Disadvantages of CISC Architecture: Disadvantages of RISC Architecture. RISC and CISC are two architectures used for designing of Advantages of CISC Architecture Disadvantages of RISC Architecture.

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In RISC architecture, the instruction set of the computer is simplified to reduce the execution time. Therefore, chip hardware and instruction set became complex with each generation of the processor. CISC designs involve very complex architectures, including a large number of instructions and addressing modes, whereas RISC designs involve simplified instruction set risx adapt it to the real requirements of user programs.

A compiler translates high level language to machine language. It has a limited number of addressing modes, typically 3 to 5.

The pipelining technique allows the processor to work on different steps of instruction like fetch, decode and execute instructions at the same time. CISC RISC It consists of a large set of instructions with variable formats Typically 16 to 64 bits per instruction It consists of small set of instructions with fixed format and these instructions are of register based instructions. It uses small and highly optimized set of instructions which are generally register to register operations.

The instructions that require register operands may take only two bytes while the instructions that require two memory addresses may take advanttages bytes.

Only load and store instructions have memory access.

RISC and CISC Architectures – Difference, Advantages and Disadvantages – Electronic Pull

It is easy to add new commands into the chip without changing the structure of the instruction set as the architecture uses general-purpose hardware to carry out commands. The main memory is divided into locations numbered from row 1: Because there are more lines of code, more RAM is needed to store the assembly level instructions.

Let’s say we want to find the product of two numbers – one stored in location 2: CISC has the ability to execute addressing modes or multi-step operations within one instruction set.


It consists of a large number of general purpose registers, typically 32 to with split data cache for instruction cache. It uses a lesser number of addressing modes. For feeding the instructions, they require very fast memory systems.

Therefore, CISC has the variable length encoding of instructions and the number of clock cycles required to execute the instructions may be varied. The ease of microcoding new instructions allowed designers to make CISC machines upwardly compatible: The data is loaded into one of four registers A, B, C, or D.

CISC design is a 32 bit processor and four bit floating point registers. This site uses cookies. When executed, this znd loads the two values into separate registers, multiplies the operands in the execution unit, and then stores the product in the appropriate register.

If the main memory is divided into areas that are fisc from row1: Typically, a large memory cache is provided on the chip in most RISC based systems. Instruction format is simple and uniform so that most instructions are abd within one cycle. There are two prevalent instruction set architectures.

RISC and CISC Architectures – Difference, Advantages and Disadvantages

Addressing modes are the manner in the data is accessed. And all three are affected by the instruction set architecture. The first level cache of the RISC processors is also a disadvantage of the RISC, in which these processors have large memory caches on the chip itself. Where, opcode is the instruction applied to load and store data, etc. However, the execution unit can only operate on data that has been loaded into one of the six registers A, B, C, D, E, or Advntages.

The major characteristics of CISC architecture are It has a large number of instructions, typically from to instructions. Complexity lies in microprogram.

Leave a Reply Cancel reply Enter your comment here The per-chip cost is reduced by this architecture that uses smaller chips consisting of more components on a single silicon wafer. Their aim is to share their knowledge about Electronics on this blog. RISC processors nad very fast memory systems to feed various instructions. The figure shown above is the architecture of RISC processor, which uses separate instruction and data caches and their access paths also different.


What is RISC and CISC Architecture with Advantages and Disadvantages

Because, the large programs need more storage, thus increasing the memory cost and large memory becomes more expensive. The operand is a memory register where instruction applied.

It has higher number of addressing modes, typically 12 to Instruction Count of the CPU. Intel — It was launched in the year and it is a CISC processor, which has instructions varying lengths from 1 to 11 and it will have instructions.

And the optimization of each instruction in the processor is achieved through pipeline technique. These cycles fetch, decode and execute of one or more instructions are overlapped advantagew this pipeline technique. In order to avoid more interactions or to reduce access time, RISC processors are provided with multiple sets of registers with optimized register usage so that frequently accessed operands are remain in high-speed storage.

In order to perform the exact series of steps described in the CISC approach, a programmer would need to code four lines of assembly: The conditional codes are set by the CISC instructions as a side effect of each instruction which takes time for this setting — and, as advahtages subsequent instruction changes the condition code bits — so, the compiler has to examine the condition code bits before this happens.

As each instruction became more accomplished, fewer instructions could be used to implement a given task.

What is RISC and CISC Architecture ? Edgefxkits

To solve these problems, the number of instructions per program can be reduced by embedding the number of operations in a single instruction, thereby making the instructions more complex. This may significantly slow down the instruction execution.

RISC processors take simple instructions and are executed within a clock cycle. The execution unit is responsible for carrying out all computations.

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