1.1 The characteristics of contemporary processors, input, output and storage devices
1.1.1 Structure and function of the processor
ALU: Performs Logic and arithmetic operations & calculations.
Control Unit: Coordinates the processor's activities.
Program Counter: Holds the memory address of the next instruction.
Accumulator: Holds part of the calculation while the ALU performs a calculation.
Memory Address Register (MAR): Holds the address in memory
Memory Data Register (MDR): Temporarily holds data moving between the processor.
Current Instruction Register (CIR): Holds the current instruction, which is split in opcode and operand.
Buses: Data, address, control
Fetch-Decode-Execute cycle.
Program Counter -> MAR: Contents of the program counter is moved into the MAR.
MAR -> MDR: Contents of addressed memory is copied to the MDR.
MDR -> CIR: Contents of MDR is copied to the CIR.
PC -> [PC] +1 / CIR is decoded & executed: The program counter increments, the CIR is executed.
Affecting CPU Performance.
Clockspeed: The rate at which the processor can perform instructions. The number of cycles in a second.
Number of cores: Multiple instructions can be performed at the same time depending on the number of cores.
Cache memory: The faster the performance if there is more cache memory as data can be fetched and stored quicker.
Pipelining: Allows the next instructions to be fetched at the same as the processor is performing operations. They are hold in a buffer.
Parallel Processing: An operation in which a process is split into parts, which are executed simultaneously on different processors on the same computer.
Von Neumann, Harvard and contemporary
processor architecture.
1.1.2 Types of processor
CISC: Does the loading, multiplication and storing in one instruction. Uses little RAM but specialised instructons have to be built into the hardware
RISC: Simple instructions each taking one clock cycle. More work to translate, more RAM and allows for pipelining RISC has largely replaced CISC but is still used in embedded systems.
Graphical Processing Units (GPU):
Parallel processing just refers to a program running more than 1 part simultaneously. Multicore processing means code working on more than one "core" of a single CPU chip.
1.1.3 Input, output and storage
Random Access Memory (RAM): Stores currently used data.
Read Only Memory (ROM): Is non-volatile, It stores the BIOS & boot up instructions for the computer.
Virtual Memory: Holds data when RAM is full. It is much slower than RAM.
Magnetic Storage: It is fast & cheap per GB. However it is not durable or portable as it has moving parts.
Optical Storage: Cheap to manufacture and portable, but has a small amount of storage.
Flash Storage: Faster than magnetic storage, it is portable and consumes less power. However it is expensive per GB and has less capacity.
Input / Output devices.
Data Bus: The data bus provides a bidirectional path for moving data and instructions between system components.
Control Bus: The purpose of the control bus is to transmit command, timing and specific status information between system components
Address Bus: It transmits the memory addresses of words that are used as operands in program instructions.
Operand: the quantity on which an operation is to be done. Opcode: is the portion of a machine language instruction that specifies the operation to be performed.
Printers
Inkjet: Works by spraying ink dots onto paper. Dot-Matrix: Pins that strike the paper in order to form an image. 3D-printers Used to print out 3D Objects.