1.1 System Architecture Flashcards
(38 cards)
Define CPU
The CPU is often thought of as the “brains” of the computer. The purpose of the CPU is to fetch, decode, and execute instructions.
Define fetch-execute cycle
The CPU fetches the next instruction from RAM, it works out what to do with the instruction, then carries out the instruction.
Define Control Unit
The control unit controls the flow of data inside the CPU (to registers) and outside the CPU to RAM and input/output devices.
Define arithmetic logic unit
The ALU does all the calculations. It completes simple addition and subtraction, as well as comparisons e.g. < >=. It also performs logical operations, e.g. AND, OR.
Define cache
The cache is very fast memory in the CPU. It is slower than the registers but faster than RAM. It stores frequently used data that the CPU can access quickly.
Define Von Neumann
Von Neumann is based on the idea of a stored program concept. Both instructions and data are stored in the same memory in binary form.
Define Memory Address Register (MAR)
The MAR holds the address of where data is to be fetched or stored.
Define Memory Data Register (MDR)
The MDR holds the data fetched from or to be written to memory (RAM).
Define program counter
The PC holds the address of the next instruction in memory.
Define accumulator
The Accumulator holds the intermediate results of calculations.
Define clock speed
This is the number of instructions a single processor core can carry out per second, e.g. desktop computers, equals 3.5 GHz (3 billion instructions per second).
Define cache size
A larger CPU cache gives the CPU faster access to frequent used instructions without having to actually use instructions from RAM. This increases performance.
Define number of cores
Each core in a CPU can process data independently. The more cores a CPU has the more instructions it can carry out at once.
Define embedded systems
Embedded systems are computers, built-in to other devices like dishwashers and microwaves. They are dedicated systems so easier to design and produce.
What is the processor?
It processes data, executes instructions, “brains of computer”, clock speed measure in cycles per second (Hertz)
What is the typical speed of a processor?
MHz or GHz
What is a core?
Executes instructions independently
What is cache?
Fast and very small amount of memory on the processor chip. The cache acts as an intermediary between the processor and the main memory. As programs are executing, the cache holds commonly used instructions. A memory cache is a memory bank that is very fast and sits between the CPU and main memory. It is faster to access than RAM.
What is clock speed?
There is an internal clock that happens on the pulse. If the clock speed increases, the faster the instructions are processed.
What is a dual core processor?
It has two processors linked together within the same integrated circuit. It should have twice the processing power, but some software has not been written with dual core processors in mind.
A quad core processor has the sam problem but double the number of processors.
What is the impact of increasing cache size?
Reduces the number of memory to disk transfers and so may speed up processing of these instructions.
When might a dual core processor be no faster than a single core processor?
If the computer is running one program, it may not be any faster as instructions still have to be carried out in a certain sequence.
What is Level 1 cache?
The data used frequently by the CPU so it is available almost instantaneously. RAM is farther away from the CPU so is much slower to receive an instruction or data from the cache.
What is level 2 cache?
Affects the performance of the CPU greatly, as this is closest to RAM and reduces wait time. Whether the cache is on the CPU board will also affect performance.
