Putting a New Spin on an Old Standard

For 25 years, the VME architecture defined COTS systems that met the demand for increases in computing and connectivity. Successive generations of new processors provided more and more compute cycles, while VME bandwidth evolved in a similar fashion from 40 Mbytes/s on the original VMEbus to 80 Mbytes/s, then 160 Mbytes/s and finally 320 Mbytes/s on 2eSST.

Structure and draft state of the VITA 46 (VPX) specification as of March 2009.
VME was also proven to be flexible in supporting a range of system sizes and many levels of ruggedization. In its familiar 6U form factor, VME found its way into small 6-slot chassis and large 21-slot systems, as well as a great many ATR and ½ ATR configurations. VME systems were created with environmental specifications running the gamut from benign commercial to almost MIL-SPEC.

A great strength of the VME community was the ability to combine technologies from many contributors into highperformance systems. This was possible because VME was a mature and unambiguous standard. But a few years ago, after an incredibly long run, the VME connector finally ran out of gas. It simply wasn't possible to coax out any more bandwidth, while processors continued to get faster. Innovations were needed to meet the need for balanced systems with ever greater processing density.

VITA, the VMEbus International Trade Association, addressed the need for a new generation of standards by pursuing two options embodied in the VXS (VITA 41) and VPX (VITA 46) standards. VXS offers higher bandwidth than VME and also a large degree of backward compatibility at the module level. The VPX standard, which was developed without the constraint of backward physical compatibility, defines a technical approach that provides support for very-high-bandwidth communications over a new highspeed connector.