Flash memory is a bang out of non-volatile memory used in computers.
Non-volatile means that the memory can store information even when the equipment is powered down.
Volatile memory (such as RAM) loses everything stored in it every time the machine itself powers down.
Flash memory comes in two distinct types NOR flash and NAND flash.
They are named for their respective logic gates.
In the case of NOR and NAND, they are named for the result they produce.
A NAND gate only ever returns the value 0 or false if all inputs into it are accurate.
Both types of flash memory design are pretty similar they use the same cell design.
The differences start at the circuit level.
Tip:NAND stands for Not-AND, a check that both inputs are not valid.
NOR stands for Not-OR, a check that is only true if neither of the information is accurate.
Contents
The History of Flash Memory
Flash was first developed in 1980 by Toshiba.
They began marketing it in 1987 as an improved version of EPROM memory.
EPROMs had to be erased before they could be rewritten and thus reused.
Note:A machine word is a measure of the largest size of memory address a computer can handle.
For a 32-bit computer, a machine word is 32-bits.
For a 64-bit computer, a machine word is 64-bits.
NOR and NAND
Modern flash memory is used in just about all modern computing devices.
NAND usually serves as general storage and is also used for data transfers.
Various digital products use NOR or NAND flash memory to store configuration data.
This specific use case was previously taken care of by EPROM or static RAd.
Modern devices deal with this issue with wear leveling algorithms and over-provisioning.
NOR memory is mainly used in cases where data integrity needs to be preserved for extended periods.
Effectively, read, write, and erase speeds are faster than NOR memory.
This makes NAND flash the superior choice for most use cases.
Additionally, NAND storage cells are physically smaller than NOR cells.
This means that NAND flash can offer greater storage density and higher performance.
NOR flash does have one advantage, though.
Being addressable by machine word, it is faster at random access and more similar to RAM.
Conclusion
Flash memory is a variant of non-volatile electrically erasable read-only memory or EEPROM.
It can be based around logical NAND gates or logical NOR gates.
NAND flash is significantly more popular than NOR flash thanks to its storage density and performance advantage.
Flashs critical advantage over its other EEPROM predecessors is that it does not need to be entirely erased.
Flashs main weakness is that memory cells can only be written several times before they wear out.
This issue is generally solved in modern devices thanks to wearing leveling algorithms and over-provisioning.
