The built-in DMA controller simplifies the process by assuming responsibility for the data transfer at far higher sustained rates than 10baseT, 100baseT, or even gigabit Ethernet. The processors are thus freed to focus on other tasks. Typical Ethernet connectivity. The transparent interconnectivity of a single host computer controlling one or more VME-bus systems is epitomized by the address space of the destination VME bus appearing to the host bus to be additional local address space. The effect is that of attaching a PC or workstation directly to the VME chassis or, conversely, inserting a VME chassis into the PC or workstation.
Memory mapping achieves transparent interconnectivity.
A typical Ethernet stack, for example, consists of application, presentation, session, transport, network, data link, and physical layers. The seven layers are present at the sending and receiving points, and processing is required at both ends. In a protocol-based transfer, one processor will build messages and send them across the cable to the processor at the other side. The second processor disassembles the messages and stores them in data memory. The interference of the protocol stacks directly affects the achievable sustained data rate, often reducing it to as low as one-third the raw data rate.