HDI-45 connector
The HDI-45 was one of Apple Computer's proprietary cable-to-onboard video connectors. This was a 45-pin connector and the HDI stood for High-Density Interconnect. These connectors were used only in the first generation Power Macintosh computers (the Power Macintosh 6100, 7100 and 8100) specifically for the Apple AudioVision 14 Display.  No other display uses this connector.  Other various Apple displays and third-party displays could be used with a special adapter that converts this unusual port to a standard DA-15 connector.

External links
 "PowerMac 6100 Graphics Hardware"
 "HDI-45 Pinout"

See also
Apple AudioVision 14 Display

Analog video connectors
Electrical signal connectors