By providing instruction-grained access to vast amounts of persistent data with ordinary loads and stores, byte-addressable storage class memory (SCM) has the potential to revolutionize system architecture. We describe a non-intrusive SCM controller for achieving light-weight failure atomicity through back-end operations. Our solution avoids costly software intervention by decoupling isolation and concurrency-driven atomicity from failure atomicity and durability, and does not require changes to the front-end cache hierarchy. Two implementation alternatives – one using a hardware structure, and the other extending the memory controller with a firmware managed volatile space, are described.