The
advantages of RISC processors:
(i)
The
performance of RISC processor is often two to four times than that of CISC
processors because of simplified instruction set.
(ii)
This
architecture uses less chip space due to reduced instruction set.
(iii)
RISC
processors can be designed more quickly than CISC processors due to its simple architecture.
(iv)
The
execution of instructions in RISC processors is high due to the use of many
registers for holding and passing the instructions as compared to CISC
processors.
(v)
The
per chip cost is reduced by this architecture that uses smaller chips
consisting of more components on a single silicon water.
Examples
of RISC processors include alpha, AVR, ARM, PIC, PA-RISC and power
architecture.
The
Disadvantages of RISC processors:
(i)
The
performance of a RISC processor depends on the code that is being executed.
(ii)
RISC
processors require very fast memory systems to feed various instructions. Typically,
a large memory cache is provided on the chip in most RISC based systems.
Advantages
of CISC processor:
(i)
Micro programming
is easy to implement and much less expensive than hard wiring a control unit.
(ii)
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.
(iii)
This
architecture makes the efficient use of main memory since the complexity of
instruction allows to use less number of instructions to achieve a given task.
(iv)
The
compiler need not be very complicated, as the micro program instruction set can
be written to match the constructs of high level languages.
Disadvantages
of CISC processor:
(i)
The
overall performance of the machine is reduced due to the different amount of
clock time required by different instructions.
(ii)
This
architecture necessitates on chip hardware to be continuously reprogrammed.
(iii)
The
complexity of hardware and on chip software included in CISC design to perform
many functions.
Examples
of CISC processor:
(a)
IBM
370/168
(b)
Intel
80486
(c)
VAX
11/780
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