The same reason Microsoft is a monopoly in the operating system market. A characteristic of a monopoly is the high barrier to entry, forbidding others to enter the market.

Intel has an agreement with AMD regarding licensing the x86 instruction set. Both manufacturers have agreements with various prebuilt computer companies and big-box retailers. Multiple companies have successful processors of various incarnations; so Intel is far from having a strict monopoly.

I would consider it more akin to, say, tissues, where everyone knows Kleenex, but there are other companies that produce tissues. (it's a horrible example, but it's the best I could come up with)

There have been recent suits against Intel regarding monopolistic practices, but most have either settled or been judged as non-monopolistic. My guess is Intel's Wikipedia page would have some info.

Actually, the x86 instruction set is now public domain, which is why VIA and other small developers are still running compliant chips out there (not in the league of AMD or Intel, though).

Intel actually purchased the AMD64 with the failure of i64 (which couldn't execute 32-bit instructions to save it's life). In all honesty, AMD itself is what has kept Intel from falling under the anti-trust knife.

Intel is not a monopoly. Intel and AMD hold basically a DUOPOLY. Intel has around 73 percent of the market while AMD has around 26 percent.

Here is a list of x86 partners: http://en.wikipedia.org/wiki/List_of_x86_manufacturers

Most of what you see outside of AMD and Intel are chips designed for specialty manufacture, like for embedded systems. VIA still has a holding on MiniITX, especially in mobile PCs, like carputers, but AMD is starting to take hold there with the Fusion line as well. Atoms are still too hot to cram into a car's dashboard.

thanks guys, very helpful for this paper