1. A method of memory tracking using copy-back, comprising: providing a redundant process controller arrangement for an industrial control system comprising a primary controller and a parallel connected redundant secondary controller both coupled by input/outputs (IOs) to actuators and sensors coupled to processing equipment, said primary controller including a primary main writable memory including a primary tracked memory region with a primary control cycle database residing therein, a primary tracking buffer and a cache data control algorithm, a primary central processing unit (CPU) with cache memory including a cache not supporting write-thru, and primary tracker logic coupled by a memory controller to said primary control cycle database in said primary tracked memory region and to said primary tracking buffer, said secondary controller including a secondary main writable memory including a secondary tracked memory region with a secondary control cycle database residing therein, a secondary tracking buffer and a secondary cache data control algorithm, a secondary CPU including a cache memory including a cache not supporting write-thru, secondary tracker logic coupled by a memory controller to said secondary control cycle database residing in said secondary tracked memory region and to said secondary tracking buffer, and a redundancy link between said primary CPU and said secondary CPU; said primary tracker logic writing tracked changes into said primary tracking buffer during each cycle, and responsive to an end of cycle notification, said algorithm: transferring said tracked changes from said primary tracking buffer to said secondary controller over said redundancy link, and writing said tracked changes to said secondary control cycle database.