AMD revolutionized the CPU market on September 23, 2003, with the launch of the Athlon 64, the first 64-bit x86 processor that maintained backward compatibility with 32-bit applications. This strategic move pressured Intel to abandon its Itanium architecture and adopt AMD's 64-bit design, leading to a significant shift in the competitive landscape of microprocessors. The Athlon 64's efficiency and performance ultimately enabled AMD to gain traction in both consumer and enterprise markets, challenging Intel's dominance.