* register content.
         * To actually enable physical responses is the job of our interrupt
         * handler which programs the physical request filter. */
-       reg_write(ohci, OHCI1394_PhyUpperBound, 0xffff0000);
+       reg_write(ohci, OHCI1394_PhyUpperBound, 0x01000000);
 
        DBGMSG("physUpperBoundOffset=%08x",
               reg_read(ohci, OHCI1394_PhyUpperBound));
 
 
        /* Register the status FIFO address range. We could use the same FIFO
         * for targets at different nodes. However we need different FIFOs per
-        * target in order to support multi-unit devices. */
+        * target in order to support multi-unit devices.
+        * The FIFO is located out of the local host controller's physical range
+        * but, if possible, within the posted write area. Status writes will
+        * then be performed as unified transactions. This slightly reduces
+        * bandwidth usage, and some Prolific based devices seem to require it.
+        */
        scsi_id->status_fifo_addr = hpsb_allocate_and_register_addrspace(
                        &sbp2_highlevel, ud->ne->host, &sbp2_ops,
                        sizeof(struct sbp2_status_block), sizeof(quadlet_t),
-                       ~0ULL, ~0ULL);
+                       0x010000000000ULL, CSR1212_ALL_SPACE_END);
        if (!scsi_id->status_fifo_addr) {
                SBP2_ERR("failed to allocate status FIFO address range");
                goto failed_alloc;