Nonvolatile Memory

While nonvolatile memory sounds like a topic only of interest to tech geeks, it is actually huge for every person in the world who uses technology of any kind. As we become exponentially more connected, people need and use more and more memory. Nonvolatile memory, which is computer memory that retrieves information even after being turned off and back on, has been used for secondary storage due to issues of cost, performance and write endurance, as compared to volatile RAM memory that has been used as primary storage. In 2016, huge strides will be made in the development of new forms of nonvolatile memory, which promise to let a hungry world store more data at less cost, using significantly less power. This will literally change the landscape of computing, allowing smaller devices to store more data and large devices to store huge amounts of information.

Definition - What does Non-Volatile Memory (NVM) mean?

Non-volatile memory (NVM) is a type of computer memory that has the capability to hold saved data even if the power is turned off. Unlike volatile memory, NVM does not require its memory data to be periodically refreshed. It is commonly used for secondary storage or long-term consistent storage.
Non-volatile memory is highly popular among digital media; it is widely used in memory chips for USB memory sticks and digital cameras. Non-volatile memory eradicates the need for relatively slow types of secondary storage systems, including hard disks.
Non-volatile memory is also known as non-volatile storage.

Volatile vs Non-Volatile Storage
In any computer system, there are two types of storage, the primary or volatile storage and the secondary or non-volatile storage. The main difference between volatile and non-volatile storage is what happens when you turn-off the power. With non-volatile storage, as long as the data has already been written, it will remain for a considerable amount of time; typically hundreds of years. Volatile memory needs constant power in order to retain the stored data. Once the power goes out, the data is also lost instantly.
The characteristics of non-volatile storage make it ideal for storing data for long term storage. Good examples of which include hard drives, memory cards, optical discs, and ROMs. Volatile storage serves a totally different purpose than non-volatile storage since it cannot be used to reliably store information. Instead, it is used by the system to temporarily hold information. This is because of the inherent speed volatile memory, which is typically thousands of times faster than most non-volatile storage. Faster is better as it prevents the creation of a bottleneck as processers get faster and faster.
Because of their very different uses, there is also a major difference in terms of capacities. Volatile memory is quite expensive per unit so typical capacities of volatile memory tend to be lower; from MBs to a few GBs. In contrast, non-volatile storage is now reaching a few TB for hard drives, and in the range of GB for most solid state drives.

Electrically addressed

Main article: Non-volatile random-access memory

Electrically addressed semiconductor non-volatile memories can be categorized according to their write mechanism. Mask ROMs are factory programmable only, and typically used for large-volume products not required to be updated after manufacture. Programmable read-only memory can be altered after manufacture, but require a special programmer and usually cannot be programmed while in the target system. The programming is permanent and further changes require replacement of the device. Data is stored by physically altering (burning) storage sites in the device.

Read-mostly devices

An EPROM is an erasable ROM that can be changed more than once. However, writing new data to an EPROM requires a special programmer circuit. EPROMs have a quartz window that allows them to be erased with ultraviolet light, but the whole device is cleared at one time. A one-time programmable (OTP) device uses an EPROM chip but omits the quartz window in the package; this is less costly to manufacture. An electrically erasable programmable read-only memory EEPROM uses electrical signals to erase memory. These erasable memory devices require a significant amount of time to erase data and to write new data; they are not usually configured to be programmed by the processor of the target system. Data is stored by use of floating-gate transistors which require special operating voltages to be applied to trap or release electric charge on an insulated control gate for storage sites.

Flash memory

Main article: Flash memory

The flash memory chip is a close relative to the EEPROM; it differs in that it can only erase one block or "page" at a time. It is a solid-state chip that maintains stored data without any external power source. Capacity is substantially larger than that of an EEPROM, making these chips a popular choice for digital cameras and desktop PC BIOS chips.
Flash memory devices use two different logical technologies—NOR and NAND—to map data. NOR flash provides high-speed random access, reading and writing data in specific memory locations; it can retrieve as little as a single byte. NAND flash reads and writes sequentially at high speed, handling data in small blocks called pages, however it is slower on read when compared to NOR. NAND flash reads faster than it writes, quickly transferring whole pages of data. Less expensive than NOR flash at high densities, NAND technology offers higher capacity for the same-size silicon.