The Pentium III 533 was the first Katmai CPU to support a FSB clocked at 133 MHz. Released on late October 1999 to compete with the newly-announced Athlon from AMD. The 533 Mhz Katmai was called "Pentium III B", "B" stands for FSB133. This Sample was produced in early April, 6 months before the official launch. Based on the kC0 core and featuring 512 KB of off-die L2 cache clocked at half the rated speed (266 Mhz).