In a magnetic disk controller equipped with a cache memory for disks, the controller in accordance with the present invention includes high order paths for data transfer between a high order channel apparatus and the cache memory through a certain one of a plurality of channel adaptors, low order...http://www.google.de/patents/US5689728?utm_source=gb-gplus-sharePatent US5689728 - Controller of paths for data transfer in system having external memory device 
