1.1 - systems architecture Flashcards
Fetch - Decode - Execute cycle
Instructions are fetched one by one from main memory, decoded, and then executed by the processor. This cycle repeats until the program is complete
CPU (central processing unit)
A chip within the computer which controls the operation of all parts of the computer and decodes then executes program instructions.
ALU (arithmetic logic unit)
The part of the CPU responsible for arithmetic and logical operations.
Cache
High speed memory built into the CPU. Instructions are copied to cache memory allowing them to be accessed more quickly and therefore increasing the speed of the CPU.
Registers
A small area of memory within the CPU where data is stored temporarily to avoid the
Von Neumann Architecture
The design on which most computers are based. It defines several registers along with the fetch - execute cycle and how the CPU interacts with main memory
MAR (memory address register)
A register. It contains the address of the instruction currently being read from or written to main memory.
MDR (memory data register)
A register. It contains the instruction which has just been copied from main memory.
PC (program counter)
A register. It contains the address of the next instruction to be fetched from memory. It is updated each time a new instruction is fetched to contain the address of the next needed instruction.
ACC (accumulator)
A register. Stores the result of the last operation.
Clock speed
How many instruction cycles the CPU can deal with in a second. Measured in MHz or GHz. Faster is better.
Cache size
The larger the amount of cache the CPU has the more instructions it can store without having to transfer to main memory and therefore the faster it will perform.
Cores
Some CPUs have more than one core, each containing its own ALU and registers and therefore capable of carrying out instructions independently. The more cores, the more instructions the CPU can process at once and therefore the faster it performs.
Embedded systems
Specialist hardware and software build into a device with a single specific purpose. They are usually found within appliances such as washing machines.
