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    Question :
    Difference between RISC and CISC
    Category Hardware and Software Design Interview Questions
    Rating (0.4) By 1256 users
    Added on 10/13/2005
    Views 4044
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    RISC-Means Reduced Instruction Set Computer.a Risc
    system has reduced number of instructions and more
    importantly it is load store architecture were
    pipelining can be implemented easily.Eg.ATMEL AVR

    CISC-Means Complex instruction set architecure.A CISC
    system has complex instructions such as direct
    addition between data in two memory locations.Eg.8085

    Submitted by H.Ranga samy (

    Features of RISC:
    Uniform instruction format, using a single word with the opcode in the same bit positions in every instruction, demanding less decoding;
    Identical general purpose registers, allowing any register to be used in any context, simplifying compiler design (although normally there are separate floating point registers);
    Simple addressing modes. Complex addressing performed via sequences of arithmetic and/or load-store operations;
    Few data types in hardware, some CISCs have byte string instructions, or support complex numbers; this is so far unlikely to be found on a RISC.

    Features of CISC:
    * complex instruction.
    * more addressing mode.
    * Highly pipelined.
    vice-versa of RISC.

    Posted by: sandeep    

    Contact sandeep Contact sandeep

    Used by Apple Used by Intel and AMD processors
    Requires less registers therefore it is easier to design Slower than RISC chips when performing instructions
    Faster that CISC More expensive to make compared to RISC
    Reduced Instruction Set Computer Complex Instruction Set Architecture
    Pipelining can be implemented easily Pipelining implementation is not easy
    Direct addition is not possible Direct addition between data in two memory locations. Ex.8085
    Fewer, simpler and faster instructions Large amount of different and complex instructions
    RISC architecture is not widely used Atleast 75% of the processor use CISC architecture
    RISC chips require fewer transistors and cheaper to produce. Finally, it's easier to write powerful optimized compilers. In common CISC chips are relatively slow (compared to RISC chips) per instruction, but use little (less than RISC) instructions.
    RISC puts a greater burden on the software. Software developers need to write more lines for the same tasks. In CISC, software developers no need to write more lines for the same tasks
    Mainly used for real time applications Mainly used in normal PC?s, Workstations and servers
    Large number of registers, most of which can be used as general purpose registers CISC processors cannot have a large number of registers.
    RISC processor has a number of hardwired instructions. CISC processor executes microcode instructions.

    Posted by: Gopi Krishnan. D    

    Contact Gopi Krishnan. D Contact Gopi Krishnan. D

    RISC-Means Reduced Instruction Set Computer.a Risc
    system has reduced number of instructions and more
    importantly it is load store architecture were
    pipelining can be implemented easily.Eg.ATMEL AVR

    CISC-Means Complex instruction set architecure.A CISC
    system has complex instructions such as direct
    addition between data in two memory locations.Eg.8085

    Posted by: NAV    

    Contact NAV Contact NAV

    risc is reduced instruction set computer .risc is cheaper than cisc because cisc consist of complex instructions,cisc stands for complex instruction set computer.risc reduces the instructions in the computer so coputer takes the speed as fast than cisc,cisc consist instruction more than risc.risc is efficient than cisc.risc& cisk are applicable for all microprocessors

    Posted by: nana banagar    

    Contact nana banagar Contact nana banagar

    in risc limietd instuction in it. and in cisc many instruction perform by one.

    Posted by: sandeep18391    

    Contact sandeep18391 Contact sandeep18391


    1.Emphasis on hardware.
    Emphasis on Software.
    2.Includes multi-clock.
    Single clock.
    3.Complex instructions.
    Reduced instructions only.
    4.Memory to memory load & store.
    Register to register load & store.
    5.Incorporated in instructions.
    Are independent instructions.
    6.Small Code Sizes.
    Large Code Sizes.
    7.High Cycles per second.
    Low cycles per second.
    8.Transistors used for storing complex instructions.
    Spends more transistors on memory registers.

    Posted by: Cheenu Gawri    

    Contact Cheenu Gawri Contact Cheenu Gawri

    The concept of RISC architecture involves an attempt to reduce execution time bye simplifying the instruction set of the computer . the major characteristics of a RISC processor are:
    1 relatively few instructions
    2 relatively few addressing modes
    3 memory access limited to load and store instructions
    4 all operations done within the registers of the CPU
    5 fixed length, easily decoded instruction format
    6 single-cycle instruction execution.
    7 hardwired rather than microprogrammed control

    A computer with a large number of instruction is classified as a complex instruction set computer,abbreviated CISC.
    Before the RISC philosophy became prominent, many computer architects tried to bridge the so called semantic gap, i.e. to design instruction sets that directly supported high-level programming constructs such as procedure calls, loop control, and complex addressing modes, allowing data structure and array accesses to be combined into single instructions. Instructions are also typically highly encoded in order to further enhance the code density

    Posted by: dev malhotra    

    Contact dev malhotra Contact dev malhotra

    risc means reduced instruction set of
    computer where as in cisc are complex
    instruction set of computer where as
    the risc is cheeper than cisc

    Posted by: Raza Muhammad khan pathan    

    Contact Raza Muhammad khan pathan Contact Raza Muhammad khan pathan

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