The x64 ISA, also known as AMD64, was introduced by AMD in 2003 as a 64-bit extension to the x86 ISA. The primary motivation behind this development was to enable computers to address more than 4 GB of physical memory, which was a significant limitation of the 32-bit x86 architecture. The x64 ISA achieved this by increasing the address bus width from 32 bits to 64 bits, allowing for a theoretical maximum of 16 exabytes (16 billion GB) of addressable memory.

The x64 ISA has also enabled the development of more powerful and efficient servers, which are critical for cloud computing, data analytics, and other applications that require high-performance processing and large amounts of memory.

CYGiSO (pronounced "cyg-ee-so") is an open-source software framework that leverages the capabilities of the x64 ISA. Developed by a team of researchers, CYGiSO aims to provide a flexible and efficient way to develop high-performance applications on x64 architectures.