The CPU
The central processing unit is a microprocessor chip that performs logical, arithmetic and control operations according to the sequence of instructions in a program.
What is the instruction set?
- The instruction set is the language which allows communication between the CPU hardware and the software. This allows each to be developed independently reducing compatibility concerns.
- Reduced instruction set computing - set of instructions that rely on a group of subroutines to perform less common operations while aiming to do so in the least processor cycles being used for each frequently used instruction.
- Complex instruction set computing is the design used by Intel on its x86 processors. This design aims to focus on backward compatibility.
Steps of work:
- Fetches instructions
- Decodes instructions
- Performs execution
- Writes back actions to be performed - which is referred to as the processor's output.
A CPU's speed is calculated in clock speed. The higher the clock speed, the more operations can be performed per second. The clock speed is referred to in Hertz (GHz).
Parts of the CPU:
- The Control Unit Directs instruction to other parts of the CPU, communicated with the ALU and registers.
- ALU (Arithmetic Logical Unit) performs integer arithmetic and bitwise operations.
- Registers are storage area on the CPU and supply ALU with operands.
What is Memory?
- hardware that stores data temporarily or permanently.
- Capacity refers to the amount of data that can be stored.
- Information is stored as a single bit (1 or 0) - 8 bits is referred to as a byte and is the smallest measurement of data.
- Capacity has exponentially increased over time, which is known as Moore's law.
Common Memory terms:
- Formatting - The process of preparing a storage device for use. It creates an indexing system that allows written data to be accessed and organized in a consistent and efficient manner.
- Reading - The process of loading data from the storage medium onto the computer's main memory.
- Writing - is the transfer of data from the main memory to a storage medium.
- Seeking - The alignment of the read/write heads over an area where data needs to be written or read.
- Access method - Sequentually is when data is looked for in a sequential manner until data is found. The direct method is when the data location is addressed and data can be accessed immediately.
RAM ( Random Access Memory):
This is also called the main memory of the computer. It is a volatile memory. Memory is made up of virtual and physical memory. Physical memory is made up of electronic chips inserted into specific memory sockets on the motherboard. RAM is physical memory that enables data - that is in use - to be accessed quicker than it would from the hard drive. Virtual memory gives the idea of unlimited RAM when the RAM's use limit is reached, the computer searches for infrequently used instructions, and copies them into the hard drive in an area called a page file.
Memory is stored in bits. Semiconductor units consist of transistors and capacitors. The capacitor holds the bit, and the transistor enables an electronic circuit to read or modify the bit.
Cache
Cache is memory that is stored just outside the CPU, Caching stores data that allows the CPU to quickly receive frequently used instructions, therefore enabling the system to operate fluently.
ROM
ROM is used in computers and devices that need data that does not or is infrequently changed. Typically, ROM keeps instruction sets referred to as firmware. Data in ROM will not be lost when power is cut (non-volatile).
Five typical measurements of data:
- Byte(B) - - 1
- Kilobyte(KB) - 1000
- Megabyte (MB) - 1 000 000
- Gigabyte(GB) - 1 000 000 000
- Terabyte (TB) - 1 000 000 000 000
