Strictly speaking MIPS Technologies produced the first 64bit CPU, then DEC then Intel announced the IA-64 architecture. The next to release one was Sun with an UltraSPARC, followed by HP, IBM then Intel actually releasing the Itanic. Of the list only IBMs PowerPCs were used in home computers (Macs) and with good reason, try to find prices on some of those
What AMD did was add 64bit extensions to x86 before Intel did.