AMD Athlon 64, Opteron, Intel Xeon with EM64T support, or Intel Pentium 4 with EM64T (all requiring SSE2 technology).
A "portable" version of software typically refers to an edition that runs without a traditional installation, often from a USB drive. System requirements for AutoCAD MEP 2010 - Autodesk autocad 2010 portable 64 bits ingles full