VGA to Macintosh Video

Passive adapter connecting an Apple Macintosh DA-15 monitor to a VGA HD-15 card, mapping RGB, sync, and sense lines across both connectors.

Updated:

This passive adapter allows an Apple Macintosh DA-15 monitor (used from the Macintosh II in 1987 through to the beige Power Mac G3 in 1998) to be connected to a standard VGA HD-15 video card. Both connectors carry analogue RGB at 0–0.7 V peak-to-peak into 75 Ω per channel, but their shell geometry and pin assignments differ: the Mac uses a two-row 15-pin D-sub (DA-15), whilst VGA uses a three-row high-density 15-pin D-sub (HD-15). The adapter routes separate HSync and VSync from the VGA card to the Mac’s /HSYNC (pin 15) and /VSYNC (pin 12) lines; /CSYNC (Mac pin 3) is left unconnected because a VGA card outputs separate sync signals and cannot drive a composite-sync line directly — Apple monitors that require only composite sync need an external sync combiner. The Mac’s three monitor-sense lines (SENSE0/1/2, pins 4/7/10) are wired to the legacy VGA monitor-ID pins (4/11/12) so that the Mac reads the appropriate 3-bit sense code and selects a compatible video mode.

15 PIN D-SUB FEMALE 15 PIN D-SUB FEMALE to the Monitor-cable

15 PIN HIGHDENSITY D-SUB MALE 15 PIN HIGHDENSITY D-SUB MALE to the Computer

DescriptionMacVGA
Red Ground16
Red21
Composite sync3n/c
Monitor Sense 044
Green52
Green Ground67
Monitor Sense 1711
No connection8n/c
Blue93
Monitor sense 21012
Sync Ground1110
Vertical Sync1214
Blue Ground138
Horizontal Sync Ground1410
Horizontal Sync1513

Notes

  • The Mac DA-15 connector is a two-row 15-pin D-sub shell, distinct from the three-row HD-15 used by VGA; the two are mechanically incompatible and require this adapter cable.
  • /CSYNC (Mac pin 3) is left unconnected (n/c) on the VGA side. A VGA card drives separate HSync and VSync; it cannot directly source composite sync. Apple monitors that accept only composite sync (such as the Apple Hi-Res Monochrome Monitor) require an external sync combiner circuit.
  • The three Mac sense lines — SENSE0 (pin 4), SENSE1 (pin 7), and SENSE2 (pin 10) — connect to VGA legacy monitor-ID pins 4, 11, and 12 respectively. The Mac reads the grounded or floating state of these lines as a 3-bit code to identify the connected display and select an appropriate video mode.
  • On DDC-era VGA monitors, VGA pin 12 carries I2C SDA (DDC). Wiring Mac SENSE2 (pin 10) to VGA pin 12 may interfere with DDC communication on DDC-capable monitors.
  • Mac pin 11 (C&VSYNC.GND / sync ground) maps to VGA pin 10 (sync ground); Mac pin 14 (HSYNC.GND) also maps to VGA pin 10.

Signals

  • Red Ground — signal ground for the red analogue video channel (Mac pin 1 → VGA pin 6).
  • Red — analogue red video, 0–0.7 V peak-to-peak, 75 Ω (Mac pin 2 → VGA pin 1).
  • Composite sync (/CSYNC) — composite sync output from the Mac DA-15; not connected on the VGA side as VGA cards supply separate sync signals.
  • Monitor Sense 0 (SENSE0) — one of three sense lines read by the Mac to identify the monitor type via a 3-bit code; connects to VGA legacy monitor-ID pin 4.
  • Green — analogue green video, 0–0.7 V peak-to-peak, 75 Ω (Mac pin 5 → VGA pin 2).
  • Green Ground — signal ground for the green analogue video channel (Mac pin 6 → VGA pin 7).
  • Monitor Sense 1 (SENSE1) — second monitor sense line; connects to VGA legacy monitor-ID pin 11.
  • No connection — Mac pin 8 is not connected on either side.
  • Blue — analogue blue video, 0–0.7 V peak-to-peak, 75 Ω (Mac pin 9 → VGA pin 3).
  • Monitor Sense 2 (SENSE2) — third monitor sense line; connects to VGA pin 12 (legacy monitor-ID bit 1; repurposed as DDC SDA on DDC-capable monitors).
  • Sync Ground — ground reference for composite and vertical sync signals (Mac pin 11 → VGA pin 10).
  • Vertical Sync (/VSYNC) — TTL-level vertical sync from the VGA card (VGA pin 14 → Mac pin 12).
  • Blue Ground — signal ground for the blue analogue video channel (Mac pin 13 → VGA pin 8).
  • Horizontal Sync Ground — additional sync ground on the Mac DA-15 (Mac pin 14 → VGA pin 10).
  • Horizontal Sync (/HSYNC) — TTL-level horizontal sync from the VGA card (VGA pin 13 → Mac pin 15).

References

Category:TV - Video - Monitor Cables