PPT: RISC & CISC | Computer Architecture & Organisation (CAO) - Computer Science Engineering (CSE) PDF Download

 Page 1


RISC and CISC
Page 2


RISC and CISC
Overview
n History of CISC and RISC
n CISC and RISC
¨Philosophy
¨Attributes and disadvantages
n Summation
Page 3


RISC and CISC
Overview
n History of CISC and RISC
n CISC and RISC
¨Philosophy
¨Attributes and disadvantages
n Summation
History of RISC/CISC
n 1950s IBM instituted a research program
n 1964 Release of System/360
n Mid-1970s improved measurement tools demonstrated on CISC
n 1975 801 project initiated at IBM’s Watson Research Center
n 1979 32-bit RISC microprocessor (801) developed led by Joel Birnbaum
n 1984 MIPS developed at Stanford, as well as projects done at Berkeley
n 1988 RISC processors had taken over high-end of the workstation market
n Early 1990s IBM’s POWER (PerformanceOptimizationWithEnhanced
RISC) architecture introduced w/ the RISC System/6k
¨ AIM (Apple, IBM, Motorola) alliance formed, resulting in PowerPC
Page 4


RISC and CISC
Overview
n History of CISC and RISC
n CISC and RISC
¨Philosophy
¨Attributes and disadvantages
n Summation
History of RISC/CISC
n 1950s IBM instituted a research program
n 1964 Release of System/360
n Mid-1970s improved measurement tools demonstrated on CISC
n 1975 801 project initiated at IBM’s Watson Research Center
n 1979 32-bit RISC microprocessor (801) developed led by Joel Birnbaum
n 1984 MIPS developed at Stanford, as well as projects done at Berkeley
n 1988 RISC processors had taken over high-end of the workstation market
n Early 1990s IBM’s POWER (PerformanceOptimizationWithEnhanced
RISC) architecture introduced w/ the RISC System/6k
¨ AIM (Apple, IBM, Motorola) alliance formed, resulting in PowerPC
What is CISC?
n CISC is an acronym for Complex Instruction Set Computer and are chips
that are easy to program and which make efficient use of memory. Since
the earliest machines were programmed in assembly language and memory
was slow and expensive, the CISC philosophy made sense, and was
commonly implemented in such large computers as the PDP-11 and the
DECsystem 10 and 20 machines.
n Most common microprocessor designs such as the Intel 80x86 and
Motorola 68K series followed the CISC philosophy.
n But recent changes in software and hardware technology have forced a re-
examination of CISC and many modern CISC processors are hybrids,
implementing many RISC principles.
n CISC was developed to make compiler development simpler. It shifts most
of the burden of generating machine instructions to the processor. For
example, instead of having to make a compiler write long machine
instructions to calculate a square-root, a CISC processor would have a built-
in ability to do this.
Page 5


RISC and CISC
Overview
n History of CISC and RISC
n CISC and RISC
¨Philosophy
¨Attributes and disadvantages
n Summation
History of RISC/CISC
n 1950s IBM instituted a research program
n 1964 Release of System/360
n Mid-1970s improved measurement tools demonstrated on CISC
n 1975 801 project initiated at IBM’s Watson Research Center
n 1979 32-bit RISC microprocessor (801) developed led by Joel Birnbaum
n 1984 MIPS developed at Stanford, as well as projects done at Berkeley
n 1988 RISC processors had taken over high-end of the workstation market
n Early 1990s IBM’s POWER (PerformanceOptimizationWithEnhanced
RISC) architecture introduced w/ the RISC System/6k
¨ AIM (Apple, IBM, Motorola) alliance formed, resulting in PowerPC
What is CISC?
n CISC is an acronym for Complex Instruction Set Computer and are chips
that are easy to program and which make efficient use of memory. Since
the earliest machines were programmed in assembly language and memory
was slow and expensive, the CISC philosophy made sense, and was
commonly implemented in such large computers as the PDP-11 and the
DECsystem 10 and 20 machines.
n Most common microprocessor designs such as the Intel 80x86 and
Motorola 68K series followed the CISC philosophy.
n But recent changes in software and hardware technology have forced a re-
examination of CISC and many modern CISC processors are hybrids,
implementing many RISC principles.
n CISC was developed to make compiler development simpler. It shifts most
of the burden of generating machine instructions to the processor. For
example, instead of having to make a compiler write long machine
instructions to calculate a square-root, a CISC processor would have a built-
in ability to do this.
CISC Attributes
The design constraints that led to the development of CISC (small amounts of
slow memory and fact that most early machines were programmed in
assembly language) give CISC instructions sets some common
characteristics:
n A 2-operand format, where instructions have a source and a destination.
Register to register, register to memory, and memory to register commands.
Multiple addressing modes for memory, including specialized modes for
indexing through arrays
n Variable length instructions where the length often varies according to the
addressing mode
n Instructions which require multiple clock cycles to execute.
E.g. Pentium is considered a modern CISC processor