Memory Hierarchy

Memory Hierarchy

The main purpose of memory hierarchy is to bridge the gap between the speed of the CPU and the slower access times of primary and secondary memory.

Two main goals to use Memory hierarchy

• To maximize access speed
• To minimize the per-bit costs

Levels

• CPU Registers: Fastest, located within the CPU itself.
• Cache Memory: Small, fast memory and stores frequently used data and instructions.
• Primary Memory: Larger, slower memory that holds actively used programs and data.
• Secondary Memory: Slowest, but offers large storage capacities for long-term data retention.
• Tertiary Storage: Very slow (slower than secondary memory), Non-volatile, Lowest cost per Bit, and Rarely used archival storage for infrequently accessed data.

Some important definitions:

·       Memory Access Time: The time it takes to locate and retrieve data from memory.

·       Memory Capacity: The amount of data that can be stored in memory.

·       Memory Latency: The delay between a request for data and its delivery.

Memory Bandwidth: The rate at which data can be transferred between memory and the CPU.