Volatile memory

Volatile memory, in contrast to non-volatile memory, is computer memory that requires power to maintain the stored information; it retains its contents while powered on but when the power is interrupted, the stored data is quickly lost.

Volatile memory has several uses including as primary storage. In addition to usually being faster than forms of mass storage such as a hard disk drive, volatility can protect sensitive information, as it becomes unavailable on power-down. Most general-purpose random-access memory (RAM) is volatile.

Types

There are two kinds of volatile RAM: dynamic and static. Even though both types need continuous electrical current to retain data, there are some important differences between them.

Dynamic RAM (DRAM) is very popular due to its cost-effectiveness. DRAM stores each bit of information in a different capacitor within the integrated circuit. DRAM chips need just one single capacitor and one transistor to store each bit of information. This makes it space-efficient and inexpensive.

The main advantage of static RAM (SRAM) is that it is much faster than dynamic RAM. Its disadvantage is its high price. SRAM does not need continuous electrical refreshes, but it still requires constant current to sustain the difference in voltage. Every single bit in a static RAM chip needs a cell of six transistors, whereas dynamic RAM requires only one capacitor and one transistor. As a result, SRAM is unable to accomplish the storage capabilities of the DRAM family. SRAM is commonly used as CPU cache and for processor registers and in networking devices.

Usage in Video Games

Commercial video games are usually sold on read-only mediums such as ROM cartridges or CD-ROMs, to stop users from inadvertently breaking their game or commit acts of piracy. However, as the 1980s came to a close and games became bigger, being able to save the current status of a game, to be picked up at a later date, became a more desirable feature.

While later consoles would see the concept of dedicated "memory cards" be used to save data, earlier cartridge-based systems had to rely on battery backups (バッテリーバックアップ) (or memory backup (メモリバックアップ ) as it was often known in Japan) - where memory would be held in RAM, and kept alive by a physical battery. Once the battery died (which, given the low power requirements is usually after several years, if not decades), a game would not be able to retain saved data when the console was turned off, however (with home consoles at least) it would not stop the game from running.

These types of system are not uncommon in electronics (most real-time clocks use a similar system), though as the price of flash memory dropped, save games in consoles such as the PlayStation were able to maintain saved states without the need for external power. Battery backup systems were prevalent in the previous generation - the Sega Mega Drive and Super NES.

The added circuitry for battery backup system added to the cost of manufacturing cartridges (which more often than not was then passed to the consumer), meaning generally such systems from this era are only seen in certain genres such as RPGs, with the rest having to make do with password systems (or no form or saving at all). When costs dropped, they were utilized for other features, such as saving high scores.

Whether a game can save is often a clue as to whether the cartridge is official - for the cost reasons described above, bootleg cartridges rarely add the battery.