Protection against unwanted I/O accesses in main storage blocks/page frames independent of any storage protection provided against unwanted CPU accesses. An I/O protection array is used containing one-bit I/O keys used only for protecting which respectively protect associated blocks/page ...http://www.google.com/patents/US5802397?utm_source=gb-gplus-sharePatent US5802397 - System for storage protection from unintended I/O access using I/O protection key by providing no control by I/O key entries over access by CP entity 
