Like its Coppermine siblings, the Pentium III 1.13GHz owes much of its performance to 256K of on-die “Advanced Transfer Cache.” Running at full processor speed and connected via a 256-bit wide data path, the cache keeps the P6 CPU core of the Pentium III well fed, even at the lofty clock of 1.13GHz. The full-speed L2 cache allows the Pentium III to scale well, without a major drop-off in performance per MHz as clock speed rises.

This was not the case with the older version Pentium III design, which carried 512K of “Discrete” cache running at half the processor speed with less efficient transfer methods. If Intel kept with the old style cache, the 1.13GHz performance would be significantly lower than it is today.

AMD has followed a similar path to the Pentium III Coppermine with their Athlon Thunderbird. The Athlon Thunderbird uses 256k of on-die full-speed L2 cache, which brings its performance level somewhat higher than the Pentium III at identical clocks. Of course, at this point, AMD's fastest is 1GHz, 133MHz behind the Pentium III 1.13GHz.

You can read more details about the ATC system in our Intel Pentium III 500E and 550E FC-PGA CPU Review.