A simple summary of memory

Recent work has been dealing with flash, reading flash, writing flash, out of obsessive-compulsive disorder to sum up.

Memory is generally divided into two categories: power loss does not lose data, power loss data loss.

1. No loss of data (ROM) terminology: non-volatile memory

ROM generally stores firmware, such as PC,BIOS. The system's bootstrap program (boot).

1. PROM in ROM (read-only memory) (programmable ROM)

Can only be erased once (each memory cell has a fuse, which can only be fused once at high temperature)

2. EPROM in ROM (read-only memory) (programmable ROM)

It can be erased more than 1000 times and erased with ultraviolet light.

3. EEPROM in ROM (read-only memory) (programmable ROM)

It can be erased many times, and it can be erased electrically, which is much better than EPROM.

4. Flash (flash memory, based on EEPROM)

Have been operating this thing recently, flash will be equally divided into several sectors (according to the size of the flash).

1) different flash has different sector sizes, and then the flash is divided into several sectors

2) different flash have different maximum read and write blocks, and the minimum is generally read and written by bytes. I have recently worked on two, one foreign maximum read and write is a sector 0x20000, and the other is Taiwan's maximum read and write 64 bytes.

5. Solid state disk (SSD, based on flash)

Solid state drives have the same status as disks, but the main difference between them is that they are faster and, of course, much more expensive.

6. Disk storage

A disk is made up of disks. Each disk has two sides, or surfaces, which are covered with magnetic recording material.

II. Power-off lost data (RAM random access memory) terminology: volatile memory

1. SRAM (static RAM)

SRAM is used to do cache (located between main memory and cpu register). The cache is divided into L1, L2, L3, level 3. L1 cache is faster than L2 cache but smaller than L2; both are static random access memory (SRAM) hardware implementations; newer processors have three levels of cache, L1.L2.L3

2. DRAM (dynamic RAM)

DRAM is used to implement main memory. Computers or mobile phones say that 1g of 4G running memory is main memory (DRAM), and 64g of 128g means hard disk / FLASH/ solid state disk.

Third, the hierarchical structure of memory

Fourth, the embodiment of each part in the equipment