types of processor Flashcards
As well as a CPU the console contains a GPU for 3D graphics. Explain why a GPU is more suitable than a CPU
for this task.
CPUs are general purpose processors
(1) whereas GPUs are designed
specifically for graphics (1). And so
likely to have built in circuitry /
instructions for common graphics
operations (1). GPUs are able to
perform an instruction on multiple
pieces of data at one time (1) often we
want to do this when processing
graphics (e.g. transforming points in a
polygon or shading pixels) (1) which
means it can perform transformations
to onscreen graphics quicker than a
CPU (1).
(i) Compare a Complex Instruction Set Computer (CISC) architecture with a Reduced Instruction Set Computer
(RISC) architecture.
CISC:
Each instruction may take multiple cycles
Single register set
Instructions have variable format
Many instructions are available
Many addressing modes are available
Complicated processor design
Integrated circuit is expensive
RISC:
An instruction performs a simple task
Limited number of instructions available
Complex tasks can only be performed by
combining multiple instructions
Simple processor design
Explain one advantage, other than cost, of RISC compared with CISC.
Programs run faster…
…due to simpler instructions
Describe one advantage to the company of using a RISC processor, rather than a CISC processor.
Costs less to design/produce.
because
- Requires less cooling to be built in.
- (If battery powered) can run off smaller
battery.
- Has fewer instructions than other
(CISC) processors.
- Simpler (circuit/hardware)
design/manufacture.
- Fewer transistors.
Explain why using a RISC processor rather than a CISC processor is likely to result in increased battery life.
- RISC has a smaller instruction set
(than CISC) - Requires fewer transistors / less
complex circuitry - Means less power is required.
Define the term ‘multicore processor’.
more than one processing unit in a
(single) processor
– …which can independently process
instructions at the same time.
Describe one difference between CISC and RISC.
Some instructions in CISC will rarely
get used …
… In RISC instructions are used
regularly
In assembly for CISC, a statement that
takes one mnemonic …
… (may) take multiple mnemonics in
RISC
Compilers for RISC need to be more
complex …
… than compilers for CISC
CISC architecture has complex
circuitry and is therefore more
expensive to manufacture…
…RISC architecture has simple
circuitry minimising manufacture cost.
- A charity has several desktop computers in their office that use a CISC processor. They are considering buying
mobile devices for their staff to use when they are not in the office.
Discuss whether these mobile devices should use the same CISC processors that are used in their desktop
computers or if they should use a RISC processor instead.
You should include the following in your answer: - the difference between each processor type
- the suitability of each processor type for mobile devices.
CISC is a complex instruction set. The
traditional approach to processor design.
Lots of instructions available although
some instructions in CISC will rarely get
used.
RISC is a reduced instruction set. A
smaller number of instructions available,
several instructions can be combined to
perform the same tasks as CISC
processors. RISC instructions are used
regularly.
RISC has fewer transistors/less complex
circuitry whereas CISC integrated circuits
are more expensive/complicated. RISC
instructions take one cycle whereas CISC
may take several. RISC can only do
complex things by combining multiple
instructions whereas CISC is done in one
line. Compilers for RISC need to be more
complex than compilers for CISC
AO2
CISC processors would run the same
software as the desktop machines. Would
be less power efficient and require larger
battery and cooling mechanisms. More
expensive to purchase.
RISC processor requires software to be
written specifically for it (cannot use CISC
instructions). More power efficient and so
requires less/no cooling and smaller
battery/longer battery life. RISC devices
may require greater RAM as programs
tend to be larger than their CISC
equivalents.
AO3
Mobile use of CISC would save money on
software and increase compatibility but
cost more to purchase and be physically
larger (heat sink/larger battery) and/or
have a shorter battery life.
RISC would require investment in software
but be cheaper to purchase and give a
better performance out of the office
(lighter/longer battery life). Some
compatibility issues may be reduced with
emulators and translators.
things about CISC
Used in laptops/ desktop computers
Has more complex hardware(more expensive)
Larger number of complex instructions of variable length
Multiple machine/ clock cycles per instruction
Physically larger, more complex circuitry, requires more silicon to make, typically more expensive
Greater energy consumption
Cant make use of pipelining
As emphasis is on the hardware, the compiler has to do less work
small code sizes, higher cycles per second
makes more efficient use of RAM than RISC
multiple addressing modes available
Stuff about RISC
Used in smartphones, tablets, embedded systems
Has simpler hardware
smaller number of simple standardised instructions that are all of a fixed length
single machine cycle per instruction
smaller in size, less complex circuitry required, less silicon, typically cheaper to produce
lower energy requirements
can support pipelining
as the emphasis is on the software, the complier has to do more work
large code sizes, lower cycles per second
heavy use of RAM
Fewer addressing modes available
