Processor Flashcards
CPU
central processing unit- the brains of the computer where most calculations take place. Data is processed and programs are executed- most important element of a computer system
what is CPU made up of
ALU, buses, dedicated registers, control unit
control unit
uses electrical signals to control and coordinate the activities and timing of the CPU, directing THE FLOW OF DATA between the CPU and other devices. It accepts the next instruction, decodes it into sequential steps and manages the executing including fetching data and addresses from registers, storing the resulting data in memory registers.
buses
a set of parallel wires of 8,16,32,64 signal lines connecting 2 or more components of a computer. They connect processor, memory and IO controllers, transferring data and signals/one part of the motherboard to another They are a shared transmission medium and only one device can transmit along a bus at any one time. control, data and address bus makes up system bus
control bus
a BIDIRECTIONAL bus sending control signals. it ensures the use and access of the other two buses by different SHARED components doesn’t mean conflict. Transmits command, timing and specific status information between system components
bus request signal
indicates a device is requesting the use of the data bus
bus grant signal
indicates the CPU has granted access to data bus
memory write
causes data in the data bus to be written into an addressed location
memory read
causes data from addressed location to be placed onto the data bus
*interrupt request
indicates a device is requesting access to the CPU
clock
used to synchronise operations
data bus
provides a bi directional path for moving data and instructions between system COMPONENTS
address bus
single direction: processor to memory/IO device. each word has its own specific address so memory address of words (used as operands in program instructions) are transmitted so data can be retrieved and sent back to the processor. Results of instruction transmitted via data bus to location
word*
memory is divided up internally into units called words. they’re a fixed size group of DIGITS: 16,32,64 bits (different processor type: different word size). Handled as a unit by the processor
ALU
performes arithmetic and logic operations on data: e.g. add, subtract, divide, multiply on fixed and floating point, shift operations (shuffling left and right), boolean: comparing, and, or, not, xor
registers*
special memory cells operating at very high speed. up to 16 general purpose in a CPU: where all ARITHMETIC, LOGIC, SHIFT operations occur
accumulator (register)*
some special purpose CPUs use a SINGLE ACCUM instead of general purpose registers to simplify design. Calculations take place here and the results of the latest calculation are held here
PC (register)
holds address of the next instruction to be executed (next instruction in sequence or address to jump to if current instruction is to jump to another. Is INCREMENTED when read. Determines SEQUENCE of instructions being read/executed
CIR
holds current instruction currently being executed, split into the opcode and operand
*MAR
hold address of the memory location from which data or instructions are to be fetched or to which data is to be written, carried by the ADDRESS BUS
MDR/MBR
data used to temporarily store data read/written to memory on the data bus from/to the processor
FDE
the sequence of operations involved in executing an instruction, the cycle is repeated as each instruction of the program is executed
fetch
retrieving an instruction from main memory
what happens during fetch
address of next instruction copied from PC to MAR
address sent down address bus
read instruction command sent down CONTROL bus
instruction sent down data bus and copied to MDR
PC incremented TO hold address of next instruction
contents of MDR copied to CIR
