soft error
A type of transient error where a signal or datum is momentarily wrong, caused for example by an ionizing particle striking a chip.
soft error: temporary glitch that fixes itself
A soft error is a transient corruption of data or logic state in electronic circuitry that occurs without permanent damage to the hardware. Unlike a hard error, which indicates physical failure, a soft error vanishes when the affected system is reset, powered down, or the erroneous value is overwritten. The circuit itself remains sound; only the information it holds has been corrupted momentarily.
The most common cause is ionizing radiation, typically high-energy particles such as cosmic rays or alpha particles emitted from trace radioactive impurities in packaging materials. When such a particle strikes a transistor's active region, it can flip a stored bit from 0 to 1 or vice versa. The larger the integrated circuit and the more densely packed its transistors, the greater the statistical probability of such strikes. Memory devices, particularly dynamic RAM and cache memory, are especially vulnerable because they store information as electrical charge in small capacitive structures.
Detection and mitigation
In critical systems, soft errors are detected and corrected through redundancy: error-correcting codes (ECC) in memory can identify and fix single-bit flips automatically; triple-modular redundancy in aerospace avionics compares three independent computations and votes on the correct result. Shielding, reduced voltage supply, and material selection also reduce the soft error rate. Modern processors operating at high clock speeds in harsh environments, such as automotive, industrial control, and space applications, face particularly acute soft error challenges.
The distinction from hard errors is operationally critical: a soft error in a single transaction may be invisible to a user or trigger a retry; a soft error rate of thousands per billion hours in consumer devices is usually tolerable noise, but in safety-critical systems, it becomes a design constraint that demands architectural safeguards. Historically, soft errors were negligible in older chips with larger geometries and lower densities, but they have become a first-order reliability concern in modern nanometer-scale processes.