computer:memory:volatile

About

When the power is removed, the memory device (storage media) is considered:

volatile memory if the data vanishes
permanent (non-volatile) memory if the data remain stored

When the data is stored on a volatile device, the data is said to be volatile

Type

Non-volatile / Permanent memory

The data will retain the stored information even if it is not constantly supplied with electric power. It is suitable for long-term storage of information. Nowadays used for most of secondary, tertiary, and off-line storage. In 1950s and 1960s, it was also used for primary storage, in the form of magnetic core memory.

List:

Disk: used for storing application permanent data
Read-only memory (ROM) (EPROM, PROM, EEPROM): used for storing firmware such as BIOS

Volatile memory

Requires constant power to maintain the stored information. The fastest memory technologies of today are volatile ones (not a universal rule). Since primary storage is required to be very fast, it predominantly uses volatile memory.

List:

Processor registers – fastest possible access (usually 1 CPU cycle), only hundreds of bytes in size
- Level 1 (L1) cache – often accessed in just a few cycles, usually tens of kilobytes
- Level 2 (L2) cache – higher latency than L1 by 2× to 10×, often 512 KiB or more
- Level 3 (L3) cache – higher latency than L2, often 2048 KiB or more
the main memory system RAM and controller cards

Table of Contents

About

Type

Non-volatile / Permanent memory

Volatile memory

Documentation / Reference