If a website promises “AutoCAD 2016 Portable 64-bit – No install – 200 MB only,” remember: if it sounds too good to be true in engineering software, it always is.
Since it doesn't install services that run in the background, it consumes fewer resources when not in use. download+autocad+2016+portable+64+bit+install
Dassault Systèmes offers DraftSight. While not portable out of the box, you can use to make your own portable version legally for personal use. If a website promises “AutoCAD 2016 Portable 64-bit
Even if a working portable version is found, it is technically inferior to the installed version: download+autocad+2016+portable+64+bit+install