The 9-pin VGA variant uses a standard DE-9 (D-sub 9-pin) shell carrying analogue RGB video signals, and predates the more familiar 15-pin HD-15 (DE-15) connector introduced with IBM VGA in 1987. Its origin is the IBM Professional Graphics Controller (PGC), released in September 1984 and documented in the IBM Technical Reference: Options and Adapters, Volume 3 (August 1984). The PGC drove analogue RGB monitors at 640×480 with 256 colours — a resolution that the later VGA standard adopted. Each colour channel has its own dedicated ground pin (pins 6–8), and a ninth pin provides a common ground for the sync and control lines.
Note: the IBM PGC original specification places a composite sync signal (combining both horizontal and vertical sync) on pin 4, and a “Professional Graphics Mode Control” signal on pin 5. Some later 9-pin VGA implementations by other manufacturers used separate horizontal and vertical sync signals on pins 4 and 5 respectively (as shown in the table below). The IBM PGC pinout and these later variants differ on pins 4 and 5.
9 PIN D-SUB FEMALE at the videocard
9 PIN D-SUB MALE at the monitor cable
| Pin | Name | Dir | Description |
|---|---|---|---|
| 1 | RED | OUT | Red Video |
| 2 | GREEN | OUT | Green Video |
| 3 | BLUE | OUT | Blue Video |
| 4 | HSYNC | OUT | Horizontal Sync |
| 5 | VSYNC | OUT | Vertical Sync |
| 6 | RGND | - | Red Ground |
| 7 | GGND | - | Green Ground |
| 8 | BGND | - | Blue Ground |
| 9 | SGND | - | Sync Ground |
Notes
- Direction is Computer relative Monitor.
- The IBM Professional Graphics Controller (1984) specifies pin 4 as a composite sync (horizontal and vertical combined) and pin 5 as the Professional Graphics Mode Control signal — not separate HSYNC/VSYNC. The table above reflects the separate-sync variant found on later 9-pin analogue RGB implementations.
- Analogue video signal levels are 0 to 0.7 V peak-to-peak into a 75 Ω load, consistent with the signal levels defined for the later IBM VGA HD-15 connector.
- Separate ground returns for each colour channel (pins 6, 7, 8) reduce cross-talk between channels.
Signals
- RED — Analogue red video signal, 0–0.7 V, 75 Ω terminated.
- GREEN — Analogue green video signal, 0–0.7 V, 75 Ω terminated.
- BLUE — Analogue blue video signal, 0–0.7 V, 75 Ω terminated.
- HSYNC — Horizontal synchronisation pulse (TTL level); on the IBM PGC this pin carries composite sync (H+V combined).
- VSYNC — Vertical synchronisation pulse (TTL level); on the IBM PGC this pin is the Professional Graphics Mode Control signal.
- RGND — Dedicated ground return for the red video channel.
- GGND — Dedicated ground return for the green video channel.
- BGND — Dedicated ground return for the blue video channel.
- SGND — Ground return for sync and control signals.