An integrated circuit device includes a nonvolatile memory, first and second buffer memories, and a controller. Each of the first and second buffer memories is configured to buffer write data to be written to the nonvolatile memory in response to a write request and also buffer read data received from the nonvolatile memory in response to a read request. A controller is provided, which evaluates the first buffer memory against at least one criterion relating to data accuracy. The controller is configured to: redirect at least some of the write data from the first buffer memory to the second buffer memory in response to the write request when the evaluation demonstrates the criterion has been exceeded, and redirect at least some of the read data from the first buffer memory to the second buffer memory in response to the read request when the evaluation demonstrates the criterion has been exceeded.