Patent ID: 8266353
Filing Date: 2012-09-11
Classification: G06F

Abstract:
1. A switch coupled between a plurality of host units and a device for communicating there between and comprising: a) a first serial advanced technology attachment (SATA) port including a first host task file, coupled to a first host unit, the first host task file responsive to commands sent by the first host unit, to the device; b) a second SATA port including a second host task file, coupled to a second host unit, the second host task file responsive to commands sent by the second host unit, to the device; c) a third SATA port including a device task file, coupled to the device, for accessing by the first or second host units, to the device, the device supports queuing of commands sent by the first and second host units and generates an original queue depth value indicative of the number of commands that the device can queue from either of the first or second host units; and d) an arbitration and control circuit coupled to the first, second and third ports, for selecting one of the first host or second host units to concurrently access the device, through the switch, by accepting the commands, from either of the first or second host units, at any given time, including when the device is not in an idle state, the arbitration and control circuit being responsive to the original queue depth value and alters the original queue depth value to an altered original queue depth value so that when the original queue value is odd, the altered original queue depth value is one half of the original queue depth value after subtracting one so that each of the first and second host units is assigned less than the number of commands indicated by the original queue depth value but that a total number of commands queued by the first and second host units remains the same as the original queue depth value thereby misrepresenting the original queue depth value to the first and second host units to be less than the original queue depth value thereby preventing the commands sent by the first and second host units from being lost by an overrun of the original queue depth value by either of the first or second host units.