VME64x

VME64x is an extension of the VMEbus standard that was developed to provide higher bandwidth and larger addressing capabilities while maintaining compatibility with existing VME equipment. It was defined in the 1990s through the VMEbus International Trade Association (VITA) and has been used across aerospace, defense, industrial automation, and laboratory instrumentation.

The key features of VME64x include support for higher speed signaling and data transfer, most notably 66 MHz operation, and provisions for a 64-bit data path (D64). It also introduces or supports an expanded addressing space with 64-bit addressing (A64) in addition to the traditional A16, A24, and A32 spaces. Optional high-speed transfer modes such as 2eVME and 2eSST are associated with VME64x to enable greater bandwidth. The standard is designed to be backward compatible with VME and VME64 devices on the same backplane, though backplanes and cards must implement the features they intend to use.

In terms of form factors and implementation, VME64x cards typically follow the same 6U and 9U Eurocard formats used by VME, with backplanes capable of carrying the enhanced signaling. The standard is commonly found in rugged, real-time systems where predictable latency and high data throughput are important.

Over time, VME64x has been complemented by newer technologies such as VXS (VME Switched Serial) and VPX, which offer further performance and architectural options. Nevertheless, VME64x remains in use for legacy systems and long-life equipment that require deterministic real-time data transfer.