RISC processor
RISC (Reduced Instruction Set Computer)
is a internal structure of a microprocessor based on a language assembler with a
minimum number of simple instructions.
The first microprocessors were based a type of
internal design CISC (Complex Instruction Set Computer) including
instructions capable of performing complex operations using single
instructions. These instructions were complex, little used and required a complex
micoprocessor core design, slowing the execution of all instructions
(including simple). The advantage of RISC is a direct
wiring of instructions within the electronic circuit, which increases the speed
treatment.
Since the Nexgen Nx586, all microprocessors are of type RISC. To keep compatibility with older microprocessors type
CISC (8088, 286, 386, 486; Pentium), A translation unit is located at the
entrance of the microprocessor. This explains why the actual speed of a current
microprocessor can not be deduced by the more clock frequency but Instead, the
performance of the decoding unit.
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CISC Advantages
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Defects CISC
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- Instructions closer to a programming language standard
- Fewer lines of code to the same result
- Write faster and more easily understandable programs
- Ram memory usage lower
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- Many different instructions, so difficult to learn
and use them all.
- Variable size instructions, with issues
regarding classification when running (non-structure standardized).
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RISC Microprocessor
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- Diffferent coding instructions for access to memory
and calculation instructions, data manupulation in the
internal registers, ...
- Internal structure that allows the processor to
execute each instruction directly (without prédécodage), this allows
using superpiline and superscalar architectures
- Many general registers.
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The transition from CISC to RISC has forced the
implementation of mathematical processor in processor core.
Related Definitions: Netburst architecture -
hyperthreading
Last update, 06/25/2011 |
