What is Flash memory?

Flash memory is the most dominant form of storage used in the world today. It comes in many form factors, shapes, and sizes. No smartphone alive today would function without one, but wait, what is flash memory?

What is flash memory?

Flash memory is an electronic non-volatile storage medium that is used to hold data permanently. It was invented in 1980 by Fujio Masuoka who was working at Toshiba.

It is designed using what are known as logic gates. On this basis, there are two types:

  1. NOR flash
  2. NAND flash

How Flash memory works

Flash memory is one of the fastest forms of storage in use today. You can find them on everything from giant servers to tiny smartphones. However, it is key to note that it is slower than static RAM.

Flash is very fast because there are no mechanical parts that need to be moved before the CPU can access data. Data on flash memory is stored electronically so the data can be saved and accessed at the snap of a finger. This is the major advantage that flash memory has over Hard disk drives.

All forms of flash storage use controllers that act as interfaces that allow computers/smartphones to read/write data to the flash memory. Since it is electronic in nature, it requires voltages to change transistor state from 1 to 0 and back to 1.

Like all other types of semiconductor technology, flash memory saved data in 1s and 0s. 1 byte of data could be saved as 10110011.

Flash memory is faster at reading data than at writing (saving) it. Whilst storage capacity, transfer speeds, and die size are very important specs for flash storage, it is the controller that is the most important part. A poor controller will cause a flash to have a reduced performance and vice versa.


Read: Storage on Smartphones Explained


Types of Flash memory

As earlier stated, there are two types of flash memory.

NOR Flash

NOR flash is a type of memory that behaves like a NOR logic gate. It is very fast and efficient. As a result, CPUs can run instructions/execute code directly from a NOR flash. The downside however is that NOR flash is expensive and has low storage capacity.

As a result, you can only find NOR flash in embedded devices, CPU cache, BIOS, etc.

NOR flash is mostly manufactured by Cypress Semiconductor Corp., GigaDevice Semiconductor, Macronix International Co. Ltd., and Micron Tech. Inc. and Winbond Electronics Corp.

NAND Flash

NAND flash behaves like a NAND logic gate. It was introduced by Toshiba in 1989. It is also very fast, efficient and has a huge data storage capacity. On the other hand, it is slower than NOR flash and is rather expensive.

NAND is slower than NOR Flash because of its architecture. Several memory cells are connected to a single gate. Now, while this increases capacity, it also reduces access times.

With that being said, it is also important to note that NAND flash is scalable and be used in lots of shapes and forms from SSDs to micro SD cards. Major manufacturers of NAND flash include Samsung, Kioxia, Western Digital, Micron, SK Hynix, and Intel.

NAND flash is used in SSDs, UFS/eUFS, MMC/eMMC, SD/micro SD, NVMe, USB flash drives, etc.


NAND vs.NOR Flash

AttributeNAND FlashNOR Flash
UseFile storage Code execution
Capacity Higher Lower
CostLowerHigher
Active power
used
Lower Higher
Standby power
used
Higher Lower
Access timeSlowerFaster
Direct CPU
execution
NoYes
Write speed FasterSlower
Read speedSlowerFaster
Reliability LowerHigher
Endurance Lower Higher

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