Contact arrangement and electronic assembly

A contact arrangement, adapted to be in a wiring board, the wiring board comprising a package substrate or a motherboard, the contact arrangement comprising:

• a plurality of contact groups, wherein at least one of the contact groups comprises:
• a plurality of shared contacts, transmitting in a first mode or a second mode signals corresponding to a first memory mode or a second memory mode;
• a plurality of dedicated contacts, transmitting the signals corresponding to the first mode and not transmitting the signals corresponding the second mode;
• and
• a plurality of ground contacts, surrounding the shared contacts and the dedicated contacts.