Flash memory is one of the main data storage technologies. Find out everything you need to know about it: definition, operation, advantages and disadvantages, different types…
First introduced in the 1980s, flash memory quickly became the most popular form of memory. a major technology of the computer industry. Today it is commonly used for data storage, especially for short and medium term storage.
It is on this technology that is based, for example, on keys or memory cardsand it can even replace computer hard drives. Here’s everything you need to know about this technology.
Flash memory: what is it?
Flash memory is a form of non-volatile memory, born from the combination between EPROM and E2PROM. This technology uses the same programming method as the standard EPROM, and the E2PROM erase method.
Compared to EPROM, one of the main advantages of this technology is that it can be electrically erased from. However, it is not possible to erase each cell of a flash memory individually unless a large amount of additional circuitry is added to the chip.
This approach greatly increases the cost, which is why most manufacturers have abandoned it. Thus, the entire chip or a large part of it is overwritten as a block or flash. This is hence the name of this technology.
How does it work?
The technology used to manufacture it is based on EEPROM (electrically erasable programmable read-only memory) chips. These are memory bank consisting of storage cellsThe data are arranged in a grid of columns and rows.
How long will this storage technology last?
When she appeared, she had a relatively short lifespan. Repeated use of the cells caused memory degradation. This is why this technology was only used for a limited number of read and write cycles.
Subsequently, however, this technology has undergone many improvements. To reduce the impact of use on storage cells, we use the wear levelling technique. Thus, it prolongs its life span. At the same time, it increases the average write record cycle from 10,000 to 100,000. This makes it possible to offer SSDs with a service life of at least five years.
Flash memory: advantages and disadvantages
Flash memory has many advantages, but also disadvantages. Depending on the use case, it is not not always the most appropriate storage technology.
One of its main advantages is that it is a non-volatile form of memory. This is what makes it ideal for short and medium-term storage. In addition, it is a handheld technology since it can take the form of keys, cards and other lightweight media. Finally, it is mechanically robust.
On the other hand, it is more expensive than the technology used in hard drives. Compared to other forms of memory, it works more slowly. In addition, its number of write and erase cycles limits use. Another defect is that the data must be deleted before new data can be written. Finally, as mentioned above, data is usually erased and written in blocks. Fortunately, costs are falling sharply with the democratisation of this technology. A 1TB SSD can easily be found for less than 100 euros, whereas it cost nearly 300 euros two or three years ago.
NAND and NOR flash memory: what’s the difference?
There are two main types of flash memory. Both types use the same basic technology, but the way they write and read data is different.
In the case of the NANDThe memory is accessed in a similar way to hard disks. When reading, the contents are first paged into the memory-mapped RAM. This is why the memory management unit is essential here.
On the contrary, the NOR flash memory is capable of reading individual memory cells, as in a traditional ROM. For erase and write functions, the commands act on the first page of the mapped memory. Note that some systems use a combination of these two types of memory.
The types of supports equipped
Several media benefit from the advantages of flash memory. These include CompactFlash cards, MultiMedia cards (MMCs), MemoryStick and Micro M2, SD, mini SD or micro SD, SHDC, SDXC, SM and xD Cards. In recent years, SSDs in 2.5-inch or NVMe M2 format, as well as eMMC models, have been used in computers and data centres.