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The mojority of the Intel and AMD cpu sales and revenues come from x86 ISA cpu sales
Intel has experimented in the past with other architectures like the i960, 860, i432 and recently with the Itanium. Some or all of them were supposed to replace the x86 architecture but none seems to have succeded. Intel also produces the XScale series (an enchancment of the StrongARM design acquired by DEC). The XScale is targeted for embedded applicatoins and has an ARM ISA
AMD on the other hand has started with the AM2901 and AMD29k cpu (a long time ago before she got the deal to license x86 designs). The only recent non-x86 cpu is the Alchemy series which uses a MIPS32 ISA, and again its target market is embedded.
There are 64bit extensions for x86 at the moment, commonly reffered to as x86-64, and yes they are considered part of the x86 family since they are backwords compatible with previous architectures.
AMD brands them as AMD64 and intel brands them as EM64T
Not all of their new processors at the moment are 64bit though. All Athlon64,Opteron,Turion models from AMD are 64bit compatible (semprons are not yet).
From intel the majority of Pentium 4 (5x1, 6xx and above are 64bit), I believe all the Xeons are 64bit too. The centrino (Pentium M) and recently announced Core Duo are not 64bit compatible. The same goes from Celeron (I heard about 64bit versions but am not sure if they are out yet)