A method for queuing hardware control blocks, such as SCBs, for a system including a system processor coupled to a plurality of host adapter devices and a buffer memory controller device by an I/O bus is based on use of an endless new hardware command block queue, and an endless done hardware command block queue. The hardware command blocks for a plurality of devices, where each device includes a device processor, are managed by forming an endless queue for a device in a memory external to the device. A first pointer to the endless queue is maintained in a memory that is not within the memory space of the device processor. A second pointer to the endless queue is maintained in a memory addressable by the device processor. The first and second pointers address the head and tail hardware command block array sites of the endless queue.