Dell Inc. remains open to using computer chips from AMD as an alternative to those of its current sole supplier, Intel Corp., but customers would have to demand it, the chief executive of the No. 1 personal computer maker said on Thursday. In what amounts to one of the PC industry"s longest-running sagas of on-again, off-again courtship, Dell Chief Executive Kevin Rollins once again revived speculation that Dell could end its long-standing refusal to use Advanced Micro Devices Inc. chips.