SAN FRANCISCO, Calif. — Intel Corp. announced it is working with a handful of companies on a specification that could push the USB's theoretical throughput beyond 4 Gbits/second, ten times its current rate. The USB 3.0 spec aims to deliver 300 Mbytes/second of usable data at the applications level and add new quality of service capabilities that could challenge the 1394 interconnect also known as Firewire.