9 PIN D-SUB FEMALE at the videocard
9 PIN D-SUB MALE at the monitor cable.
The IBM Enhanced Graphics Adapter (EGA), introduced in 1984, extends the 9-pin DE-9 TTL direct-drive standard established by the CGA by adding a second pair of colour bits, yielding 6-bit RrGgBb encoding and a palette of 64 colours. The adapter supports two horizontal scan rates — 15.7 kHz for CGA-compatible and standard EGA colour modes, and 21.85 kHz for the enhanced EGA high-resolution mode — and carries all signals at standard TTL levels (0.0–0.6 V low, 2.4–3.5 V high). In addition to the DE-9 video output, the EGA provides a 6-pin Berg-strip light-pen interface on the card. The adapter is fully documented in the IBM Technical Reference: Options and Adapters Volume 2 (April 1984).
| Pin | Name | Description |
|---|---|---|
| 1 | GND | Ground |
| 2 | SR | Secondary Red |
| 3 | PR | Primary Red |
| 4 | PG | Primary Green |
| 5 | PB | Primary Blue |
| 6 | SG/I | Secondary Green / Intensity |
| 7 | SB | Secondary Blue |
| 8 | H | Horizontal Sync |
| 9 | V | Vertical Sync |
Signals
- GND — Signal and chassis ground.
- SR — Secondary Red; the low-order red bit in 6-bit RrGgBb encoding. In CGA-compatibility mode this pin carries the Intensity signal.
- PR — Primary Red; the high-order red bit.
- PG — Primary Green; the high-order green bit.
- PB — Primary Blue; the high-order blue bit.
- SG/I — Secondary Green in native EGA mode (low-order green bit); acts as Intensity in CGA and MDA compatibility modes.
- SB — Secondary Blue; the low-order blue bit. Carries no signal in CGA or MDA emulation modes.
- H — Horizontal Sync; 15.7 kHz in CGA/standard EGA colour modes, 21.85 kHz in enhanced EGA mode.
- V — Vertical Sync.
Notes
The monitor mode table below (from the Sony CPD-1303 user guide) shows how the same nine pins are interpreted across compatible signal standards:
Standard EGA according to the CPD-1303 user guide:
| Mode | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|
| Analog | GND | GND | RED | GRN | BLU | GND | — | H/HV | V |
| DIG/NORM | GND | GND | RED | GRN | BLU | GND | — | H/HV | V |
| D1 | GND | GND | RED | GRN | BLU | INT | — | H/HV | V |
| D2 / CGA | GND | GND | RED | GRN | BLU | INT | — | H/HV | V |
| D2 / MDA | GND | GND | — | — | — | INT | GRN | H/HV | V |
| D2 / EGA | GND | r | R | G | B | g | b | H/HV | V |
Lower-case letters on the EGA line denote the secondary (low-intensity) colour bits; upper-case are the primary colour bits.
- r/g/b denotes the secondary (low-order) colour bits that give EGA its 64-colour palette.
- * Sync on green is automatic if H or HV is not assigned to pin 8.
- All signal lines operate at TTL levels: logic low 0.0–0.6 V, logic high 2.4–3.5 V.
- The EGA card holds 64 KB of video memory in four 16 KB bit planes, expandable to 256 KB.
- The DE-9 shell at the card is female (socket); the monitor cable terminates in a male (plug).