1.1 Systems Architecture Flashcards
CPU
Central Processing Unit - The main part of the computer, consisting of the registers, ALU and control unit.
Fetch-execute cycle
The complete process of retrieving an instruction from store, decoding it and carrying it out. Also known as the instruction cycle.
ALU
Arithmetic Logic Unit - Performs calculations e.g. X = 2 + 3 and logical comparisons e.g. IF x > 3 in the CPU.
CU
Control Unit - Decodes instructions. Sends signals to control how data moves around the CPU.
Cache
Memory in the processor providing fast access to frequently used instructions and data.
Register
Tiny areas of extremely fast memory located in the CPU normally designed for a specific purpose, where data or control information is stored temporarily e.g. MAR, MDR etc.
Von Neumann Architecture
Traditional computer architecture that forms the basis of most digital computer systems. Instructions are fetched, decoded and executed one at a time.
MAR
Memory Address Register - Holds the address of data ready for use by the memory data register, or the address of an instruction passed from the program counter. Step 2 of the fetch, decode, execute cycle.
MDR
Memory Data Register - Holds the data fetched from or to be written to the memory. Step 3 of the fetch, decode, execute cycle.
Program Counter
Holds the address of the next instruction to be executed. Step 1 of the fetch, decode, execute cycle.
Accumulator
Holds the result of calculations.
Clock Speed
Measured in Hertz, the clock speed is the frequency at which the internal clock generated pulses. The higher the clock rate, the faster the computer may work. The “clock” is the electronic unit that synchronizes related components by generating pulses at a constant rate.
Cache Size
A part of the main store between the central processor and the rest of the memory. It has extremely fast access, so sections of a program and its associated data are copied there to take advantage of its short fetch cycle. The larger the size of the cache the more that can be copied and stored without having to go back to the RAM, this has significant impact on the speed of processing.
Cores
A part of a multi-core processor. A multi-core processor is a single component with two or more independent actual CPU’s, which are the units responsible for the fetch, decode, execute cycle.
Embedded System
A computer which has been built to solve a very specific program and is not easily changed. For example the operating system placed inside a washing machine, microwave or set of traffic lights.
