VME64

VME64 is a 64-bit data width extension of the VMEbus computer bus standard, developed as part of the VMEbus family to provide higher throughput and larger addressable memory for embedded and industrial systems. Introduced in the early 1990s, VME64 retains the basic VME signaling and backplane concepts while adding support for a 64-bit data path (D64) and a 64-bit address space (A64). It is designed to be compatible with existing VME hardware and software, offering continued access to the wider ecosystem of VME boards and backplanes.

Key features of VME64 include the ability to transfer 64 bits of data per bus cycle, alongside the existing 16- and 32-bit data modes used by earlier VME variants. It also expands addressing options through 64-bit address spaces (A64) in addition to the traditional A16, A24, and A32 spaces. Command and control signaling use address modifiers to select the appropriate space, enabling memory, I/O, and configuration access in a unified framework. The standard supports common VME concepts such as bus arbitration, interrupt signaling, and block transfer modes (BLT/MBLT) for high-throughput data movement.

Physical form factors for VME64 boards follow the established VME Eurocard sizes (for example, 6U and 3U). Backplanes and connectors are generally compatible with existing VME infrastructure, with VME64 cards able to operate in VME environments that implement the widened data and address paths. Variants such as VME64x later extended the feature set while preserving backward compatibility with VME64 hardware.

Applications for VME64 include defense, aerospace, industrial control, and scientific instrumentation where large address spaces and high data bandwidth are advantageous. The standard remains part of the broader portfolio of VMEbus solutions used for rugged, real-time computing.