The default Linux behaviour on an NMI of either memory or unknown is to continue operation. For many environments such as scientific computing it is preferable that the box is taken out and the error dealt with than an uncorrected parity/ECC error get propagated.

If an unrecoverable ECC error or unknown non-maskable interrupt (NMI) is detected and the value of this tunable is set to 1, then the kernel will panic and halt the system.