RISC vs CISC | RISC | Reduced Instruction Set Computer | CISC | Complex Instruction Set Computer
Summary
TLDRThis video offers a comprehensive comparison between RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer) architectures. It explains the fundamental differences in instruction set size, instruction fetch time, and design philosophy. The video clarifies that RISC has a fixed, smaller set of instructions leading to simpler and faster execution, whereas CISC features a larger, more complex set allowing for more compact code. It also touches on aspects like addressing modes, the number of registers, compiler design, and the suitability of each architecture for specific types of operations, concluding with the advantages and disadvantages of both.
Takeaways
- đ RISC stands for Reduced Instruction Set Computer and CISC for Complex Instruction Set Computer, highlighting the fundamental difference in the number and complexity of instructions.
- đ RISC has a fixed instruction size, whereas CISC's instruction size varies based on the complexity of the instruction.
- â± In RISC, the instruction fetch time is consistent for all instructions, while in CISC, it varies depending on the instruction's complexity.
- đ RISC has a smaller and simpler instruction set compared to CISC, which has a larger and more complex set with a variety of instructions.
- đ RISC is based primarily on register-to-register operations, while CISC includes a wider range of memory-based instructions.
- đ RISC has fewer addressing modes due to its focus on register operations, whereas CISC offers more modes due to its memory-based instructions.
- đȘ RISC has more registers within the CPU, as it relies heavily on register-to-register operations, while CISC has fewer due to its reliance on complex instructions.
- đ ïž Compiler design is simpler for RISC due to its smaller and simpler instruction set, whereas it's more complex for CISC due to its larger and more complex set.
- đ RISC results in longer program sizes because simple instructions require more steps to perform tasks, while CISC has shorter programs due to the availability of complex instructions.
- đą The number of operands in RISC is fixed, mainly involving registers, while in CISC, the number of operands varies with the instruction, involving both registers and memory.
- đ§ RISC uses a hardware control unit due to its fixed and simple instruction set, making it faster, while CISC often uses micro-programmed control units due to the complexity of its instructions.
- đ Execution speed is generally faster in RISC due to efficient pipelining facilitated by fixed instruction size, whereas CISC faces inefficiencies due to variable instruction size and the need for frequent pipeline flushes.
Q & A
What does RISC stand for in computer architecture?
-RISC stands for Reduced Instruction Set Computer. It is a design approach that uses a smaller set of simple instructions with a fixed instruction size.
What is the full form of CISC in the context of computer design?
-CISC stands for Complex Instruction Set Computer. It features a larger set of complex instructions with varying instruction sizes.
Why is the instruction size fixed in RISC architecture?
-The instruction size is fixed in RISC architecture to simplify the design and improve the efficiency of instruction fetching and pipelining.
How does the instruction fetch time differ between RISC and CISC architectures?
-In RISC, the instruction fetch time is constant for all instructions due to the fixed instruction size. In CISC, the fetch time varies depending on the complexity of the instruction.
What is the typical size and complexity of the instruction set in RISC and CISC architectures?
-The instruction set in RISC is small and simple, while in CISC it is large and complex, with a variety of instructions available.
How does the number of addressing modes compare between RISC and CISC architectures?
-RISC architecture has fewer addressing modes, mostly because most instructions are based on registers. CISC, on the other hand, has more addressing modes due to its complexity and variety of instructions involving both registers and memory.
Why does RISC architecture have more registers in the CPU?
-RISC architecture has more registers because it relies heavily on register-to-register operations, which simplifies the design and execution of instructions.
What is the typical complexity of compiler design for RISC and CISC architectures?
-Compiler design is simpler for RISC due to its small and simple instruction set. For CISC, compiler design is more complex due to the large and complex instruction set and the variety of addressing modes.
Why is the program size typically longer in RISC architecture compared to CISC?
-The program size is longer in RISC because its simple instructions require more steps to perform complex tasks, whereas CISC can perform the same tasks with fewer, more complex instructions.
How does the number of operands in instructions differ between RISC and CISC architectures?
-In RISC, the number of operands is typically fixed, often involving registers and memory. In CISC, the number of operands can vary depending on the instruction, which can involve a mix of registers and memory.
What is the typical control unit design for RISC and CISC architectures?
-RISC typically uses a hardware control unit due to its fixed and simple instruction set, which allows for direct execution. CISC often uses a micro-program-controlled unit due to the complexity of its instruction set, which requires more elaborate control mechanisms.
Why is execution speed generally faster in RISC compared to CISC?
-Execution speed is faster in RISC because of the uniform instruction size, which allows for efficient pipelining. In CISC, the variable instruction size can lead to inefficient pipelining and the need to flush the pipeline more frequently, slowing down execution.
Which type of operations are RISC and CISC architectures more suitable for?
-RISC is more suitable for dedicated operations due to its fixed and simple instructions, while CISC is more suitable for a variety of operations due to its complex instructions that can handle different tasks more efficiently.
Outlines
đ€ Introduction to RISC and CISC Architectures
This paragraph introduces the concepts of Reduced Instruction Set Computer (RISC) and Complex Instruction Set Computer (CISC) architectures. The speaker explains that RISC has fewer and simpler instructions, while CISC features a larger set of complex instructions. The video promises to delve into the design philosophies and differences between the two, providing insights into instruction size, fetch time, set size, addressing modes, and the number of registers involved. It sets the stage for a comprehensive comparison based on various parameters.
đ Deep Dive into RISC and CISC Characteristics
The second paragraph delves deeper into the characteristics of RISC and CISC architectures. It discusses the simplicity and fixed instruction size of RISC, which leads to a smaller and simpler instruction set, fewer addressing modes, and a higher number of registers within the CPU. In contrast, CISC is characterized by its variable instruction size, larger and more complex instruction set, a greater variety of addressing modes, and fewer registers due to its reliance on complex instructions. The paragraph also touches on compiler design, program size, code density, the number of operands, control unit complexity, execution speed, and the suitability of each architecture for specific types of operations. It concludes with the advantages of RISC in pipelining and its suitability for dedicated operations, whereas CISC is better for varied operations due to its complex instruction set.
Mindmap
Keywords
đĄRISC
đĄCISC
đĄInstruction Set
đĄInstruction Size
đĄInstruction Fetch Time
đĄAddressing Modes
đĄRegisters
đĄCompiler Design
đĄProgram Size
đĄPipelining
Highlights
Basic comparison between RISC (Reduced Instruction Set Computer) and CISC (Complex Instruction Set Computer) architecture is discussed.
RISC has fewer instructions in the set compared to CISC which has more complex instructions.
Instruction size in RISC is fixed, while it varies in CISC depending on the complexity of the instruction.
RISC has the same instruction fetch time for all instructions, whereas in CISC it varies based on instruction complexity.
RISC's instruction set is small and simple, while CISC's is large and complex with a variety of instructions.
RISC is based on load and store operations, whereas CISC has a variety of complex instructions concerning memory.
RISC has fewer addressing modes due to its reliance on registers, while CISC offers more due to its complexity.
RISC has more registers inside the CPU, as it is based on register execution, while CISC has fewer due to its complexity.
Compiler design is simpler for RISC due to its small set of instructions, while it's complex for CISC.
Program size tends to be longer in RISC due to its simple instructions, while it's shorter in CISC with complex instructions.
RISC has a fixed number of operands, mainly in registers, while CISC has variable operands including memory.
RISC uses a hardware control unit for its fixed and simple instructions, while CISC uses micro-program controlled due to complexity.
RISC offers faster execution speed due to efficient pipelining, while CISC's variable instruction size leads to inefficiencies.
Pipelining is more effective in RISC due to its fixed instruction size, while it's less effective in CISC.
RISC is more suitable for dedicated operations, while CISC is suitable for a variety of operations due to its complex instructions.
The major advantage of CISC is its better code density compared to RISC.
Transcripts
welcome to engineering Funda family in
this video I'll be discussing basic
comparison in between risk and cisk
architecture my dear students risk means
reduced instruction set computer and
cisk means complex instruction set
computer so risk is having less number
of instruction in set of computer and in
cisk you'll be having complex
instruction so there will be many
instruction in set of computer but when
we talk about both of these computers
design then there are many things that
you need to know with respect to
different parameters I'll explain you
each and everything with respect to
different parameter in this video so I
can give you guarantee after watching
this video you'll be having exit idea
about what is risk what is cisk and how
design philosophy is there behind risk
and cisk so my dear students here when
we talk about risk and cisk then first
of all you should know what what is the
basic full form which is there with risk
it is reduced instructions at computer
and cisk is complex instruction set
computer so with risk you'll be having
less number of instruction in computer
and with cisk you'll be having many
instruction along with complex
instruction in computer Here My Dear
students you should know instruction
size with risk it is fixed right while
with cisk it varies with respect to
instruction for complex instruction size
of instruction will be more and for
simple instruction size of instruction
will be less right so Here My Dear
students size of instruction varies with
respect to operation in CIS but it is
almost fixed with all the instructions
with risk Right Here My Dear students
instruction fetch time that is also same
for all the instruction with risk but
instruction fetch time that varies with
respect to instruction in cisk as if you
have complex instruction in that case
you need to have more instruction fetch
time and for simple instruction it will
take less time to fetch the instruction
right so based on complexity instruction
fetch time that is even changing with
respect to cisk architecture while with
risk you'll be observing it is Con
instant for almost all the instructions
Right Here My Dear students when we talk
about instruction set then it will be
small and simple for risk right but with
cisk it will be large and complex there
are varieties of instructions will be
available right there will be more
memory kind of instructions that will be
available with cisk with risk
instruction set that will be purely
based on resistors only right as risk is
there based on load and store and and
CIS is not there based on load and store
right so as cisk is not there based on
load and store varieties of complex
instructions are available with respect
to memory but risk architecture that is
there based on resistors only right so
small and simple instructions will be
there with risk architecture my dear
students addressing modes will be less
with risk architecture why the reason is
most of the instructions are based on
resistors only right so less addressing
modes will be there and here with cisk
many addressing modes will be there why
the reason is cisk architecture is
having instructions based on resistors
as well as memory so when you operate
with varieties of modes with respect to
memory you'll be having many other modes
while with risk we don't have many modes
with respect to memory right we just
have load and store mode with respect to
memory so less number of modes will be
there in terms of addressing mode and
CIS is having more addressing mode right
my dear students when we talk about
number of resistors then risk will be
having many resistors inside CPU while
with CIS it will be having few resistors
why the reason is risk architecture that
is based on resistors execution only and
CIS architecture that is based on
complexity of instructions right so here
you don't need to have many resistors
you will be operating with memory right
so inside memory you can store the data
and you can operate along with
instructions while with risk you'll be
performing almost all the operations
with respect to resistors so you should
have many resistors in Risk architecture
Right Here My Dear students when we talk
about design of compiler then it will be
simple with risk why the reason is we
have small set of instructions right and
when we talk about cisk architecture its
compiler design will be complex why the
reason is instruction set is complex
many addressing modes are there so your
compiler design will be complex with
cisk
architecture Here My Dear students when
we talk about program size then it will
be long with risk architecture why the
reason is we have simple instructions it
is based on resistors only right so to
perform any particular task you'll have
to write many instructions so your
program size will be long in cisk we'll
be having small program why the reason
is we are having complex instructions
right and because of complex
instructions are available by writing
few instructions only we can perform
program right so you'll be observing
risk architecture is having weak code
density with respect to program and CIS
architecture that is having better code
density better code density means less
number of instructions are there in
given program right while with risk
you'll be having more instructions for
same program that's why we code density
will be there my dear students when we
talk about number of operants then that
is fixed with risk architecture mainly
it will be there in resistors only why
the reason is most of the instructions
are there with respect to resistors only
and load and store is happening with
risk architecture right so one operand
that will be resistor only second
operand could be Memory but it will be
having fixed number of operands when we
talk about cisk architecture operants
varies with respect to instructions it
can be resist it can be Memory right so
you'll be observing variable operant are
there for simple instructions you may
have resistors as a operant but for
complex instruction you may be having
resistors as well as memory as a operand
right my dear students when we talk
about control unit then Hardware control
unit is there with risk why the reason
is instruction set is fixed it is having
simple instruction so we can have
hardwire control right but with cisk if
you provide Hardware control then it
will be very costly right so here we
will be having control unit with micro
program controlled right so here
Hardware control that will be faster
compared to micro program controlled
with cisk that you should know right as
Hardware will provide direct execution
in micro program micro program will get
executed and it will control that right
here when we talk about execution speed
then risk is very fast compared to cisk
why the reason is here instruction size
is same because of that you can have
efficient pipelining here instruction
size is different so you can have
inefficient pipelining in pipelining in
parallel we can execute many instruction
here because of inefficient pipelining
you need to flush the pipelining
frequently in that case your execution
will be slower right only major
advantage which is there with CIS that
is better code density compared to risk
that one can say Right Here My Dear
students as I have told you pipelining
is more effective with risk and it will
be less effective with cisk right why
the reason is variable size instruction
will insert bubble in the pipelining and
in Branch execution you'll be observing
that you'll have to flush the pipeline
right so cisk is having more bubbles in
the pipeline risk is having less bubble
in the pipeline that's why risk is
effective in pipelining and my dear
students when we talk about processor
then you should know this risk is more
suitable for dedicated operation and
cisk that is more suitable for varieties
of operation why it is more suitable for
varieties of operation the reason is
complex instructions are there with risk
you have fixed and simple instructions
so you will have to perform dedicated
operation using risk but as if you have
varieties of operation then you should
go for for cisk so that is how risk and
cisk are there and this is how design
philosophy is there I hope it is clear
to you still if any quer is there what I
want is you just post that in comment
box to have discussion with me thank you
so much for watching this video
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