Back in the dim and distant past, Intel made a processor called the 386. It was their first 32 bit processor and Intel created a procesor development team to create a 64 bit processor called the Itanium with assistance from HP.
Intel would be creating a different kind of processor to what they had in the past. HP had noticed the limitations on the machine language used inside the current processors and a technology developed from Yale University was used instead.
The Itanium found its place in High Performance Computing, where parallel computing and super computing can use the advanced features in the Itanium to their advantage.
The big downside was that the Itanium's native instruction set was not compatible with Intel's so called x86 instruction set that Intel had used since the early PCs.
Intel's rival, AMD created the Opteron which was far less radical than the Itanium, it used the x86 instruction set and extended it to work in 64 bit mode. This meant their procesor could run in 16 bit, 32 bit and 64 bit modes of operation. Intel decided to use this approach for their future processors starting with the late model Pentium 4.
Intel continued to manufacture the Itanium under licence from HP until this year when the licence has expired.