It defines a fixed rear I/O pin assignment that focuses on modern, fast serial point-to-point connections.
The CompactPCI definition for 6U double Eurocards includes additional connectors (J3, J4, J5) for rear I/O.
Fast serial point-to-point connections have become the state-of-the-art technology and are gradually replacing the classic bus architecture in computers.
As a result, several manufacturers tried to implement their own rear I/O concepts using the J2 connector, but had no standard to make their J2 pin assignments compatible with other cards.
It stays compatible with but extends the existing standard by a new definition of the rear J2 connector, adding a number of serial interfaces to provide fast and standardized rear I/O also on 3U format.
This connector supports high frequencies of 5 Gbit/s, even when mated with the CompactPCI-standard unshielded 2-mm hard-metric headers.