CameronDev , 7 days ago

AMD were already using the x86 ISA long before amd64.

en.m.wikipedia.org/wiki/AMD

Intel had introduced the first x86 microprocessors in 1978.[51] In 1981, IBM created its PC, and wanted Intel’s x86 processors, but only under the condition that Intel also provide a second-source manufacturer for its patented x86 microprocessors.[12] Intel and AMD entered into a 10-year technology exchange agreement

AMD were also second source for some other Intel logic chips before that deal.