The Pentium III[2] (marketed as Intel Pentium III Processor, informally PIII or P3) brand refers to Intel's 32-bit x86 desktop and mobile CPUs based on the sixth-generation P6 microarchitecture introduced on February 28, 1999.[citation needed] The brand's initial processors were very similar to the earlier Pentium II-branded processors. The most notable differences were the addition of the Streaming SIMD Extensions (SSE) instruction set (to accelerate floating point and parallel calculations), and the introduction of a controversial serial number embedded in the chip during manufacturing. The Pentium III is also a single-core processor.