Competition in the market for low-cost PCs will soon intensify as Intel Corp. and Advanced Micro Devices Inc. ready faster versions of their value microprocessors. Intel will spearhead its attack by bringing its Pentium 4 Willamette processor core to the Celeron line this quarter. This will allow Intel to continue the Celeron's clock frequency upswing from 1.3GHz to a range of 1.4 to 1.6GHz and even higher, according to Nathan Brookwood, an analyst at InSight64 Inc., Saratoga, Calif. �The P3 Celeron core has reached its upper clock speed limit. By using the P4 NetBurst architecture of the original Willamette core, Intel can extend Celeron frequencies ever higher,� Brookwood said. Intel acknowledged that it will continue to increase the performance of its Celeron line, but declined to elaborate. AMD, meanwhile, confirmed that it will fight back by extending its performance model numbering scheme to its value-end Duron line. Sources agreed that AMD will push frequencies up a notch when the company introduces its first 0.13-micron Appaloosa and Thoroughbred cores this quarter for the Duron and Athlon processors, respectively.