Intel was pretty insistant on its 64-bit CPU, called the Itanium, being the future now. Other 64-bit CPUs -- Alpha, HP-PA, and MIPS -- were shut down, because Intel held the future with its Itanium. (The sole holdout is IBM's PowerPC, used in the Apple Mac.)
Problem Itanium was pure 64-bits, and had poor (read: slow) compatibility with today's 32-bit computing world. Intel convinced some vendors to believe that Itanium was it. Hardware vendors spent actual money designing 64-bit computers, while some CAD software vendors talked about supporting it. (To be fair, Intel recommends 64-bit CPUs only to those whose applications benefit from more than 4GB memory -- like CAD.)
Intel's scrawny competitor, AMD, made like an iceberg against the (T)Itanic [as 'The Inquirer' nicknames it] with its hybrid 32/64-bit Opteron. It ran 64-bit apps fast, and 32-bit apps faster. The secret? Opteron is compatible with the Pentium and its predecessors, while the Itaniumc is not. While it matters not to hardware vendors, software vendors intensely dislike maintaining more than one codebase (hence the hold Microsoft has on the market).
After fighting a failing battle, Intel is now talking of its own x86-compabile 32/64-bit CPU. This is history repeating itself, notes Nebojsa Novakovic: "Just remember the i860 15 years ago, or the i432 25 years ago. Both were high-profile CPU announcements with unusual architectures and big promises. They did some damage to the competition (after all, the first WinNT port was supposedly on i860), and then they gently faded away, to see parts of them reincarnated in follow-on x86 CPUs from Intel."