It was developed to provide a cost-efficient solution to a complete multimedia system.
Using Media Bus cards for building a system reduced slot requirements and compatibility problems.
[1] Expansion cards supporting this interface were only manufactured by Asus for a very limited time.
While similar to PCI-X in appearance, the extension contains 4 additional pins (2 on each side) for a total of 68.
The divider between the PCI slot and Media Bus extension is too wide to support a properly-keyed PCI-X card.