Overview/History of Architecture
By the late 20th century, Intel's x86 processors (running on IA-32 architecture) were obsolete compared with modern design and technology. In the 1970's, the IA-32 architecture was designed around a relatively small number of transistors. Intel decided to design a new processor architecture based around the ability to fit several million transistors on a single chip. The result was the IA-64 architecture, developed jointly with Hewlett-Packard.
This new architecture was first used in a processor called the Itanium, unveiled in May 2001. The Itanium ran at up to 800 MHz, but it's performance compared to equivalent x86 processors was only a slight improvement. And while the architecture was backward compatible with IA-32 instruction, it's performance of running that instruction was actually worse!
Intel and HP attempted to correct the problems in their next model, the Itanium 2, first released in June 2002. The Itanium 2 improved its performance, and several new versions released over the next couple of years continued to improve the architecture.
Rich Instruction Set
Large Register Files
Modulo Scheduled Loops
Cache Control Instructions