It was IBM who forced Intel and AMD to sign the agreement. From CNET: "Early 1980s--IBM chooses Intel's so-called x86 chip architecture and the DOS software op

It was IBM who forced Intel and AMD to sign the agreement. From CNET: "Early 1980s--IBM chooses Intel's so-called x86 chip architecture and the DOS software operating system built by Microsoft. To avoid overdependence on Intel as its sole source of chips, IBM demands that Intel finds it a second supplier. 1982--Intel and AMD sign a technology exchange agreement making AMD a second supplier. The deal gives AMD access to Intel's so-called second-generation "286" chip technology."