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This paper introduces CODA, a novel approach to mitigate the ColumnDisturb error, which causes bitflips in victim rows due to activations in aggressor rows. By implementing three variants鈥擟ODA-E, CODA-F, and CODA-G鈥攖his method significantly reduces the rate of Adjacent-Counter Increments (ACI) required for effective mitigation, achieving reductions of 12x to 1300x. The key finding is that CODA allows for the toleration of ColumnDisturb without incurring any performance or power overhead, addressing a critical limitation in existing solutions.
CODA slashes the overhead of mitigating ColumnDisturb by up to 1300x, enabling error tolerance without performance penalties.
ColumnDisturb is a new data-disturbance error in which activations to an aggressor row cause bitflips in a victim row located hundreds of rows away (intra-subarray bitflips) and in victim rows in adjacent subarrays (inter-subarray bitflips). Intra-subarray ColumnDisturb can be tolerated by solutions (such as SALT and REGA) that operate at subarray granularity. However, to tolerate inter-subarray ColumnDisturb, such solutions must be extended with ColumnDisturb Protection (CDP), which performs additional {\em Adjacent-Counter Increment (ACI)} for the neighboring subarrays. The ACIs ensure that adjacent subarrays also undergo mitigation, even if they receive no demand activations. Unfortunately, because ACIs occur at a 200\% rate relative to demand activations, they effectively increase the activations perceived by the bank to 3x, which causes significant slowdowns (17\% at a TRHD of 500) and refresh overheads. The goal of our paper is to tolerate ColumnDisturb while incurring negligible overheads. We propose CODA, a ColumnDisturb mitigation that significantly reduces the rate of ACI required to securely tolerate ColumnDisturb. We present three variants of CODA. First, CODA-E (Evade), which leverages the insight that ACI can be skipped if the neighboring subarray receives a demand activation, and reduces ACI by 2x. Second, CODA-F (Fraction), which uses the timing duration of ColumnDisturb to do only a fractional increment for ACI, thereby reducing the rate of ACI by 2x-16x. Finally, CODA-G (Gangskip), which operates at multi-subarray granularity and skips ACI for neighboring subarrays within the same gang, further reduces overall ACI by 2x-8x. Overall, CODA reduces ACI by 12x-1300x, thereby making it possible to tolerate ColumnDisturb while incurring zero performance and power overhead.
