The Apple Macintosh DA-15 video connector (a two-row 15-pin D-sub shell, introduced with the Macintosh II in 1987 and used through the beige Power Mac G3 in 1998) carries the same analogue RGB signal levels as VGA — 0–0.7 V peak-to-peak into 75 Ω per channel — but adds composite sync (/CSYNC) on pin 3 and uses pins 4, 7, and 10 as three-bit monitor sense lines (SENSE0/1/2) rather than video data. The VGA HD-15 connector (a three-row high-density 15-pin D-sub shell introduced by IBM with the PS/2 family in 1987) carries separate horizontal and vertical sync on pins 13 and 14 with TTL-level signals. This passive adapter maps the RGB pairs across both connectors, routes Mac /CSYNC (pin 3) to VGA pin 13 to serve as the composite sync or horizontal sync input, and wires the Mac sense lines to the legacy VGA monitor-ID pins so that the Mac outputs 640×480 video. Mac pin 15 (/HSYNC) is intentionally left unconnected because /CSYNC on pin 3 already carries composite sync to VGA pin 13.
15 PIN D-SUB MALE to the Computer
15 PIN HIGHDENSITY D-SUB FEMALE to the Monitor-cable
| Description | Mac | VGA |
|---|---|---|
| Red Ground | 1 | 6 |
| Red | 2 | 1 |
| Composite sync | 3 | 13 |
| Monitor Sense 0 | 4 | 4 |
| Green | 5 | 2 |
| Green Ground | 6 | 7 |
| Monitor Sense 1 | 7 | 11 |
| No connection | 8 | n/c |
| Blue | 9 | 3 |
| Monitor sense 2 | 10 | 12 |
| Sync Ground | 11 | 10 |
| Vertical Sync | 12 | 14 |
| Blue Ground | 13 | 8 |
| Horizontal Sync Ground | 14 | n/c |
| Horizontal Sync | 15 | n/c |
Notes
- The Mac DA-15 shell is a two-row D-sub; the VGA HD-15 shell is a three-row high-density D-sub — they are mechanically incompatible and not interchangeable.
- Mac /CSYNC (pin 3) is routed to VGA pin 13 (HSync/CSync), supplying composite sync to the monitor. Mac /HSYNC (pin 15) is left unconnected for the same reason.
- The sense lines (Mac pins 4, 7, 10) connect to legacy VGA monitor-ID pins (4, 11, 12). The VGA monitor grounds these ID pins, which the Mac reads as a three-bit code to select 640×480 output.
- Mac SENSE2 (pin 10) maps to VGA pin 12, which DDC-era monitors use as the I²C SDA line for EDID. On DDC-capable monitors this connection may interfere with DDC communication.
- The Mac LC differs from the Mac II and IIci in that it does not carry vertical sync mixed into pin 5 (green video); on the LC, vertical sync is on pin 12 only.
Signals
- Red Ground — analogue ground for the red video channel (Mac pin 1 → VGA pin 6)
- Red — analogue red video, 0–0.7 V p-p, 75 Ω (Mac pin 2 → VGA pin 1)
- Composite sync — /CSYNC, TTL active-low composite sync; routed to VGA HSync/CSync input (Mac pin 3 → VGA pin 13)
- Monitor Sense 0 (SENSE0) — three-bit monitor identification line 0; the VGA monitor grounds VGA pin 4 (legacy Monitor-ID bit 2), asserting a binary 0 (Mac pin 4 → VGA pin 4)
- Green — analogue green video, 0–0.7 V p-p, 75 Ω (Mac pin 5 → VGA pin 2)
- Green Ground — analogue ground for the green video channel (Mac pin 6 → VGA pin 7)
- Monitor Sense 1 (SENSE1) — three-bit monitor identification line 1; the VGA monitor grounds VGA pin 11 (legacy Monitor-ID bit 0) (Mac pin 7 → VGA pin 11)
- No connection — Mac pin 8 is not connected on either side
- Blue — analogue blue video, 0–0.7 V p-p, 75 Ω (Mac pin 9 → VGA pin 3)
- Monitor Sense 2 (SENSE2) — three-bit monitor identification line 2; the VGA monitor grounds VGA pin 12 (legacy Monitor-ID bit 1, DDC SDA in modern monitors) (Mac pin 10 → VGA pin 12)
- Sync Ground — return ground for composite sync and vertical sync signals (Mac pin 11 → VGA pin 10)
- Vertical Sync — /VSYNC, TTL active-low vertical sync (Mac pin 12 → VGA pin 14)
- Blue Ground — analogue ground for the blue video channel (Mac pin 13 → VGA pin 8)
- Horizontal Sync Ground — ground reference for the horizontal sync circuit; not connected on the VGA side (Mac pin 14 → n/c)
- Horizontal Sync — /HSYNC; left unconnected because composite sync on pin 3 is used instead (Mac pin 15 → n/c)