Characteristics of RISK and CISK
Ans:-
RISC/CISC Characteristics (PowerPC) RISC Technology
Modern programmers use assembly:
• for hand coding for speed
• for debugging
Common features of CISC:
• many
instructions that access memory directly
•
large number of addressing modes
•
variable length instruction encoding
•
support for misaligned accesses
Common RISC characteristics
• Load
/store architecture (also called register-register or RR
Architecture ) which fetches operands and results
indirectly from
main
memory through a lot of scalar registers.
Other architecture
is
storage-storage or SS in which source operands and final
results
are retrieved directly from memory.
• Fixed length instructions which
(a) are easier to decode than variable length
instructions, and
(b) use fast, inexpensive memory to execute a
larger piece of
code.
• Hardwired controller instructions (as opposed
to micro coded
instructions). This is where RISC really shines as hardware
implementation
of instructions is much faster and uses less silicon
real
estate than a micro store area.
• Fused or compound instructions which are
heavily optimized for
the
most commonly used functions.
• Pipelined implementations with goal of executing one
instruction
(or more)
per machine cycle.
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