Püsivälu

Püsivälu is a Finnish term used in information technology to denote non-volatile memory, i.e., memory that retains stored data when power is removed. It contrasts with volatile memory such as DRAM or SRAM, which require continuous power to maintain contents.

The term is formed from pysyvä meaning permanent and muisti meaning memory. In contemporary ICT literature, püsivälu is commonly used to refer to technologies that provide persistent storage and memory, allowing data to persist across power cycles.

Common technologies classed as püsivälu include ROM-based memories (ROM, PROM, EPROM, EEPROM), and flash memory used in solid-state drives and memory cards. The category also encompasses emerging non-volatile memories such as MRAM (magnetoresistive RAM), PCM (phase-change memory), and FRAM (ferroelectric RAM). Some devices combine volatile and non-volatile regions, using non-volatile memory to store firmware, bootloaders, or critical configuration data.

Key properties to consider include retention time, write endurance (number of write cycles), density, access speed, and power consumption. Non-volatile memory can be byte-addressable (as in some FRAM or MRAM) or block-addressable (as in flash).

Applications range from firmware storage and embedded systems to long-term data storage in SSDs and memory cards. Ongoing research seeks to increase write speeds and endurance, improve density, and reduce cost and energy usage while expanding the roles of püsivälu in computing architectures.