<Tr> <Th> Predecessor </Th> <Td> Pentium II </Td> </Tr> <Tr> <Th> Successor </Th> <Td> Pentium 4, Xeon, Celeron, Pentium M </Td> </Tr> <P> The Pentium III (marketed as Intel Pentium III Processor, informally PIII) brand refers to Intel's 32 - bit x86 desktop and mobile microprocessors based on the sixth - generation P6 microarchitecture introduced on February 26, 1999 . The brand's initial processors were very similar to the earlier Pentium II - branded microprocessors . The most notable differences were the addition of the SSE instruction set (to accelerate floating point and parallel calculations), and the introduction of a controversial serial number embedded in the chip during the manufacturing process . </P> <P> Similarly to the Pentium II it superseded, the Pentium III was also accompanied by the Celeron brand for lower - end versions, and the Xeon for high - end (server and workstation) derivatives . The Pentium III was eventually superseded by the Pentium 4, but its Tualatin core also served as the basis for the Pentium M CPUs, which used many ideas from the P6 microarchitecture . Subsequently, it was the Pentium M microarchitecture of Pentium M branded CPUs, and not the NetBurst found in Pentium 4 processors, that formed the basis for Intel's energy - efficient Core microarchitecture of CPUs branded Core 2, Pentium Dual - Core, Celeron (Core), and Xeon . </P>

When was the intel pentium iii processor introduced