A block transfer, however, is possible for DMA style applications. The bus allows multiple masters, and contains a powerful interrupt scheme. A resource manager is required to handle the interrupts. The VME bus is a TTL based backplane which, although the system is asynchronous, sets the data transfer speed to approximately 20 Mbytes per second. Read, write, modify and block transfers are supported.
Data transfer is asynchronous supporting modules with a broad variety of response times.
The system is modular and follows the Eurocard standard. VME card cages contain 21 slots, the first of which must be used as a crate manager. The usual card sizes are 160 x 216 mm and 160 x 100 mm. Cards of both sizes can be mixed in the same crate. The smaller cards are capable of 8 or 16 bit transfers.