Twenty-five years ago, AMD introduced the Athlon XP family, built on the Palomino core. The processors were competitive in real-world performance but ran at lower clock speeds than Intel's Pentium 4 line, which was winning the marketing battle over megahertz. To counter that, AMD launched its Performance Rating system, pairing the chips with labels like "1800+" and the slogan "Performance matters more than MHz."
Tom's Hardware's tests from October 2001 backed AMD's approach. The Athlon XP 1800+ was able to beat Intel's flagship Pentium 4 2 GHz in the majority of benchmarks, and the Athlon XP running at 1533 MHz could reach or beat a Pentium 4 running at almost 33% higher clock speed. The original editor, Thomas Pabst, noted that AMD wisely undersold its chips with the PR naming and had little alternative given the clock-speed gap.
The PR system was abandoned roughly five years later. Intel lost its big MHz advantage when it moved from Pentium 4 Netburst to Pentium M and Core chips, and AMD's Athlon 64 was well received on its own merits. By then, CPU marketing had shifted toward multi-core counts, making clock-speed-based ratings irrelevant.