The desktop 64-bit processor should have been released by Intel in August 2004. Three processors were released at the same time, including Pentium 4 3.2F-3.4F-3.6F
The server 64-bit technology was first used in the Xhiqiang DP 2.8E in June 2004.
X86-64 is an extension technology of the X86 system and a technical means proposed by Intel. AMD's 64-bit technology is called AMD64. In order to respect intellectual property rights, most detection software uses X86-64 instead of its name. AMD currently does not own or license its use under its standards consortium.
AMD’s first recorded desktop use probably started with the Athlon 64 280 (754) processor in April 2004.
It was proposed by Intel. . . I'm too lazy to find the specific information readily available.