When a computer specification lists “16GB memory,” it usually refers to volatile memory, which loses its contents the moment power is cut. Non-volatile memory, by contrast, retains data even after the device is powered down. This basic distinction explains why saved files remain on an SSD when a computer is shut off, while the open applications disappear.
Volatile Types: DRAM and SRAM
Most system RAM is dynamic random-access memory, or DRAM. Each DRAM cell uses a capacitor and a transistor to store a bit, but the charge in the capacitor leaks over time. The system must refresh this data repeatedly while running. Once power stops, the stored information vanishes. Mobile devices often use low-power variants like LPDDR5X, while desktops have moved to DDR5. Even unified memory designs, such as those found in AMD’s Ryzen AI Max chips, rely on this same temporary storage method despite having physical forms that differ from traditional DIMM sticks.
Static random-access memory, or SRAM, is also volatile but does not need the periodic refresh cycles required by DRAM. SRAM uses latching circuitry with several transistors per bit, which makes it faster. This speed makes it ideal for processor caches, where small amounts of frequently accessed data sit close to the CPU. A processor might have hundreds of megabytes of SRAM cache, but this still operates on a much smaller scale than the gigabytes of DRAM used for main memory.
Non-Volatile Storage and Flash
Non-volatile memory handles information that must remain available when the device loses power. The most common example in consumer hardware is NAND flash, which powers SSDs, USB drives, and memory cards. An SSD contains flash memory paired with a controller that manages reads, writes, and error correction. The controller spreads write operations across different memory cells to prevent some parts from wearing out faster than others. This setup applies to both SATA and NVMe drives.
NOR flash is another form of non-volatile memory, but it is typically used for code rather than large files. It can store firmware that starts the hardware and loads the operating system. Processors in embedded devices can often run code directly from NOR flash without first copying it to RAM. This shows that “non-volatile” describes a property of the memory rather than a single type of component, just as DRAM and SRAM are both volatile while serving different roles.
Opening a photo-editing app illustrates how modern devices move data between these types of memory. The app and saved photo begin on non-volatile storage. The system loads the code and data it needs into DRAM. The processor’s caches then keep copies of frequently accessed information closer to the CPU, reducing how often it must reach back into main memory. None of those temporary copies need to survive a normal shutdown, but what you save eventually reaches non-volatile storage.
Hibernation makes the distinction clear. Windows writes the contents of volatile memory to a hibernation file on non-volatile storage before powering DRAM down. When the computer resumes, Windows reads that file and restores the memory contents. This differs from sleep mode, where the session remains in RAM and is lost if the power goes out. A specification like “16GB memory” describes the volatile resource for active tasks, while the SSD provides the space for data that must persist after the power is removed. Cache clearing does not guarantee faster devices, highlighting that different storage technologies serve distinct purposes.