While Autodesk does not officially release portable versions, community-created versions of AutoCAD 2012 are often sought after because:
Downloading AutoCAD from unofficial sources through "portable links" carries significant risks: autocad portable 2012 64 link
A "portable" app is typically a repackaged version of software designed to run without being formally installed on a host operating system. It usually lives in a single folder or on a USB drive. autocad portable 2012 64 link
Many users prefer the 2012 interface and its introduction of features like associative arrays and multifunctional grips. Risks of Using "Portable" Links autocad portable 2012 64 link
Older versions like 2012 generally require less RAM (minimum 2GB for 64-bit) than modern releases.