Systems architecture 1.1 Flashcards
CPU
Central Processing Unit: “The main part of the computer, consisting of the registers, ALU and control unit.”
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.”
PC
Program Counter: “Holds the address of the next instruction. Step 1 of the fetch, decode, execute cycle.”
Accumulator
“Holds the result of calculations.”
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.”
F-D-E cycle
Fetch-Decode-Execute Cycle: “The complete process of retrieving an instruction from store, decoding it and carrying it out. Also known as the instruction cycle.”
Clock Speed
“Measured in Hertz, the clock speed is the frequency at which the internal clock generates pulses. The higher the clock rate, the faster the computer may work. The “clock” is the electronic unit that synchronises 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 here without having to go back to slower main memory (RAM), this has a 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 CPUs, which are the units responsibly 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.”
