35 pin Apple ADC “MicroCross” female connector at the Apple computer.
35 pin Apple ADC “MicroCross” male connector at the cable.
The Apple Display Connector (ADC) is a proprietary Apple interface introduced in July 2000 with the Power Mac G4 and G4 Cube. It combines DVI-format TMDS digital video, analogue RGB video, USB 1.1, soft-power control, and a 25 V DC supply (up to 4.0 A, 100 W) through a single 30-pin plus five-coax “MicroCross” connector, eliminating the need for separate power and USB cables between computer and display. Apple used ADC exclusively on its flat-panel Cinema Displays and the final ADC-equipped Power Mac G4 towers before discontinuing the interface in June 2004 when the aluminium Cinema Displays adopted standard DVI.
| Pin | Function | Pin | Function |
|---|---|---|---|
| 1 | 25V Supply | 16 | T.M.D.S. Data1/3 Shield |
| 2 | 25V Supply | 17 | T.M.D.S. Data3- |
| 3 | LED | 18 | T.M.D.S. Data3+ |
| 4 | T.M.D.S. Data0- | 19 | DDC Clock |
| 5 | T.M.D.S. Data0+ | 20 | Clock Return |
| 6 | T.M.D.S. Data0/5 Shield | 21 | USB Data+ |
| 7 | T.M.D.S. Data5- | 22 | USB Data- |
| 8 | T.M.D.S. Data5+ | 23 | USB Return |
| 9 | DDC Data | 24 | T.M.D.S. Data2- |
| 10 | Vertical Sync | 25 | T.M.D.S. Data2+ |
| 11 | 25V Return | 26 | T.M.D.S. Data2/4 Shield |
| 12 | 25V Return | 27 | T.M.D.S. Data4- |
| 13 | Soft Power | 28 | T.M.D.S. Data4+ |
| 14 | T.M.D.S. Data1- | 29 | Clock+ |
| 15 | T.M.D.S. Data1+ | 30 | Clock- |
| MicroCross Pins | |||
| Pin | Function | ||
| C1 | Analog Blue Video | ||
| C2 | Analog Green Video | ||
| C3 | Analog Horizontal Sync | ||
| C4 | Analog Red Video | ||
| C5 | Analog RGB Return and DDC Return |
Signals
- 25V Supply / 25V Return — 25 V DC power rail delivered by the host to the display; maximum current 4.0 A (100 W total). Pins 1 and 2 carry the supply; pins 11 and 12 carry the return.
- T.M.D.S. Data0± – Data5± — Transition Minimised Differential Signalling (TMDS) data pairs, compatible with the DVI single-link or dual-link digital video protocol. Shields are shared between adjacent pairs (Data0/5, Data1/3, Data2/4).
- Clock± / Clock Return — TMDS pixel clock differential pair (pins 29–30); Clock Return (pin 20) provides the reference ground for the clock channel.
- DDC Data / DDC Clock — Display Data Channel (I²C bus) used to read the display’s EDID data for plug-and-play capability. DDC Data on pin 9; DDC Clock on pin 19.
- Vertical Sync — Vsync signal from host to display (pin 10).
- LED — Control signal for the display’s status LED (pin 3).
- Soft Power — Signal allowing the display to request a host power state change, enabling one-button power on/off (pin 13).
- USB Data+ / USB Data- / USB Return — USB 1.1 downstream port signals (pins 21, 22, 23) routing USB from the host to the display’s built-in USB hub.
- C1 – C4 (Analogue video coaxes) — Analogue RGB video: C1 = Blue, C2 = Green, C3 = Horizontal Sync, C4 = Red.
- C5 (Analogue RGB Return and DDC Return) — Shared return coax for the analogue video signals and DDC bus.
Notes
The ADC connector is Apple-proprietary and carries both digital TMDS video and analogue RGB video simultaneously, making its signal complement functionally similar to the VESA P&D-A/D standard, though the connector and protocol are entirely Apple-specific and the two are not electrically compatible.
The 25 V DC supply (pins 1–2, max 4.0 A) is unique to ADC; no VESA or DVI standard carries DC power at this voltage. Third-party DVI-to-ADC adapters require an external power brick to supply this voltage, as a DVI source provides only +5 V on its DDC supply pin.
ADC displays accept digital video input from the TMDS pairs and will not operate from an analogue-only (VGA) source. Connection from a DVI-D or DVI-I graphics card requires a powered adapter (such as the Apple DVI to ADC Adapter, part number M8661LL/A) that converts the 25 V rail and relays USB.
The interface was introduced in July 2000 and discontinued in June 2004 when Apple transitioned to standard DVI connectors on the aluminium Cinema Display lineup.