The Apple Display Connector (ADC)
The Apple Display Connector (ADC) is Apple's proprietary modification of the DVI (Digital Visual Interface) connector that combines analog and digital video signals, USB, and power in a single cable. Apple's goal was to reduce cable clutter and simplify the process of connecting a new monitor to a Mac. This was especially nice with monitors that included a built-in USB hub.
The problem with ADC is that it was a proprietary standard. Apple introduced it with the "Mystic" Dual Processor Power Mac G4 and new ADC monitors in July 2000, removing the industry standard DVI port found on the "Sawtooth" Power Mac G4. ADC remained a standard feature of Power Macs through the 2004 Power Mac G5; ADC was not present on the 2005 Power Mac G5, and Apple resumed use of the DVI connector alongside ADC with the "Mirror Drive Door" Power Mac G4 in August 2002.
Apple sold a DVI-to-ADC adapter for US$149 that allowed Macs with DVI output to use ADC displays. The adapter connected to the DVI port, a USB port, and a power cable to provide everything and ADC monitor needed.
Third-party vendors were quick to realize an opportunity here, as four generations of G4 Power Macs had analog VGA plus ADC but no DVI ports. ADC-to-DVI adapters (prices today start at about US$30) make it possible to use industry standard displays with non-ADC G4 Power Macs or use a second DVI display with video cards that included both ADC and DVI, as most of these video cards support dual monitors. There are also ADC-to-VGA adapters that allow users to connect a standard VGA monitor to an ADC port.
Part of the ADC legacy is that Apple still uses a single "ganged" cable for its displays, which includes DVI, power, USB, and FireWire.
Other than being proprietary, ADC had two other drawbacks: It could only provide 100W of power, which limited it to 17" CRT displays and wasn't enough for 30" LCD monitors, and the pins Apple used on the AGP connector were later designated for use with AGP 8x video cards, which is why pins 3 and 11 must be disabled on these cards before they will work in any AGP Power Mac G4 except the Sawtooth model.
- Apple Display Connector, Wikipedia
- Apple Display Connector, Apple Developer Connection
- Pins 3 and 11: How and Why to Disable Pins 3 and 11 on AGP 8x cards in your Power Mac G4, The Mac Elite
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