MEMORY HEIRACHY
Memory heirachy is about arranging different kinds of storage devices in a computer based on their size,cost and access speed and the roles they play in application processing.
This theory proposes that cortical columns at every level of the heirachy can learn complete models of objects over time and that features are learned at specific locations on the objects .
There are two types of memory heirachy:
1. External memory or secondary memory: Comprising of magnetic disk,optical disk and magnetic tape i.e peripheral storage devices which are accessible by the processor via an I/O module.
2. Internal memory or Primary memory: Comprising of main memory,cache memory and cpu registers.This is directly accessible by the processors.
Memory heirachy design :
1. Registers:
- Registers are small, high-speed memory units located in the CPU.
- They are used to store the most frequently used data and instructions.
- Registers have the fastest access time and the smallest storage capacity, typically ranging from 16 to 64 bits.
2. Cache memory:
- Cache memory is a small, fast memory unit located close to the CPU.
- It stores frequently used data and instructions that have been recently accessed from the main memory.
- Cache memory is designed to minimize the time it takes to access data by providing the CPU with quick access to frequently used data.
3. Main memory:
- Main memory also known as RAM (Random Access Memory), is the primary memory of a computer system.
- It has a larger storage capacity than cache memory, but it is slower.
- Main memory is used to store data and instructions that are currently in use by the CPU.
Types of main memory:
Static RAM: Static RAM stores the binary information in flip flops and information remains valid until power is supplied. It has a faster access time and is used in implementing cache memory.
Dynamic RAM: It stores the binary information as a charge on the capacitor. It requires refreshing circuitry to maintain the charge on the capacitors after a few milliseconds. It contains more memory cells per unit area as compared to SRAM.
4. Secondary Storage:
- Secondary storage, such as hard disk drives (HDD) and solid-state drives (SSD), is a non-volatile memory unit that has a larger storage capacity than main memory.
- It is used to store data and instructions that are not currently in use by the CPU.
5. Magnetic Disk:
- Magnetic Disks are simply circular plates that are fabricated with either a metal or a plastic or a magnetized material.
- The Magnetic disks work at a high speed inside the computer and these are frequently used.
6. Magnetic Tape:
- Magnetic Tape is simply a magnetic recording device that is covered with a plastic film.
- It is generally used for the backup of data.
