SLR02 - Types of Processors

What is an instruction set?

• Set of all instructions written in machine code that can be recognised + executed by CPU

• CISC, RISC

CISC

• Complex Instruction Set Computers: Aims to complete task in as few lines as possible

• Could includes complex instruction

• Less common today

RISC

• Reduced Instruction Set Computer: aims to use simple instructions that will be executed within single clock cycle

• Need to separate complex instructions into simpler commands

Characteristics of CISC

• Used un laptops / desktop computers

• Complex hardware

• Emphasis on hardware, compiler less work to do

• Physically larger, more silicon, more expensive

• Greater energy consumption

• Large num complex instructions

• Multiple clock cycles per instruction

• Can’t make use of pipelining

• Smaller code size, high cycles per second

• Makes more efficient use of RAM than RISC

• Multiple addressing modes available

Characteristics of RISC

• Used in smartphones, tablets, embedded systems

• Simpler hardware

• Smaller size, less complex, less silicone, cheaper produce

• Low energy required

• Emphasis on software = compiler more work

• Heavy use of RAM

• Smaller num simple, instructions of fixed length - standardised

• Single machine cycles per instruction

• Larger code size, lower cycles per second

• Can support pipelining

• Fewer addressing made available

CISC vs RISC

Multicore processor

Single processor chip containing multiple independent processing units called cores

CMPS

Chip multiprocessors - manufacturers integrate cores onto a single physical chip as a CPU - actually a CMP containing multiple CPU cores

Performance of a multicore processor is further enhanced by

• One chip shared cache

• Inter-core communication

Limitations of multicore

• Overheads involved with inter-core communications

• Some programs can’t make maximum use of all cores

Parallel processing

The processing of program instructions by dividing them between multiple cores, while one processor fetching instruction, separate unit decoding previous, other unit executing

What limits parallel processing

• Task being carried out

• If software designed for parallel processing

Co-processor

• Additional processor used for a specialised task

• To improve overall speed of computer by executing concurrently with the main CPU

Difference between CPUs & GPUs

• CPUs excel at performing complex operation on small data sets

• GPUs better for simpler operation on large data sets

Why are GPUs good at rendering graphics?

GPU able to carryout thousands of floating-point operation much quicker due to the benefits of its bespoke design for parallel processing

Other uses of GPUs

• Any situation that requires processing thousands of simple calculations on multiple points of data performed quicker on GPU, e.g.:

  • Oil exploration

  • Machine Learning

  • Statistical analysis