The Macintosh Centris and Quadra frame buffer determines what type of display is attached to the video connector by examining the state of 3 sense line pins. The following chart details how these three pins must be wired for each of the supported display types. For each supported display, the screen resolution (horiz. pixels X vertical pixels), bandwidth, and the vertical and horizontal scan rates are listed.
The Macintosh Quadra series and the Macintosh Centris series should support any display, whether from Apple or from another vendor, that meets one of the following specifications:
STANDARD SENSE CODES:
| Display | Sense pins
10 7 4 | Hor x Vert
(Pixels) | Band Width
(MHz) | Vert
Refrsh (Hz) | Horiz
Refrsh (KHz) |
| Apple 21 Color | 0 0 0 | 1152 x 870 | 100 | 75 | 68.7 |
| Apple Portrait | 0 0 1 | 640 x 870 | 57.2832 | 75 | 68.9 |
| 12" AppleColor RGB | 0 1 0 | 512 x 384 | 15.6672 | 60.15 | 24.48 |
| Apple 2-Page Mono. | 0 1 1 | 1152 x 870 | 100 | 75 | 68.7 |
| NTSC | 1 0 0 | underscan
512 x 384 | 12.2727 | 59.94 | 15.7 |
| 1 0 0 | overscan
640 x 480 | 12.2727 | 59.94 | 15.7 |
| To produce a color NTSC signal, a RGB-to-NTSC converter is required. |
|
12" Apple High-Res
Monochrome | 1 1 0 | 640 x 480 | 30.24 | 66.7 | 35.0 |
13" AppleColor
High-Res RGB | 1 1 0 | 640 x 480 | 30.24 | 66.7 | 35.0 |
| Apple 16" Color Disp. | (See Note 4) | 832 x 624 | 57.63 | 75 | 49.7 |
Portrait Color,
such as Radius | 1 0 1 | 640 x 870 | 57.2832 | 75 | 68.9 |
NOTES:
1. Sense pins 4, 7, and 10 are referred to as MON.ID1, MON.ID2, and MON.ID3 in the Macintosh Quadra pinout table or SENSE0, SENSE1, and SENSE2 in pinout tables for the video connectors.
A sense pin value of 0 means that pin should be grounded to the C&VSYNC.GND signal; a value of 1 means do not connect the pin.
2. Extended sense codes will be examined if the following sense code is detected: 1 1 1.
3. The terms 'underscan' and 'overscan' are used to describe the active video resolution for NTSC and PAL modes. Underscan means that the active video area appears in a rectangle centered on the screen with a black surrounding area. This ensures that the entire active video area always is displayed on all monitors. Overscan utilizes the entire possible video area for NTSC or PAL. However, most monitors or televisions will cause some of this video to be lost beyond the edges of the display, so the entire image will not be seen.
4) The Apple 16" Color Display should have pins 4 and 10 tied together and pin 7 should be unconnected. If used with a Macintosh Display Card, the Apple 16" Color Display also requires the Macintosh Display Card 4*8, 8*24, or 8*24 GC with revised ROMs.
EXTENDED SENSE CODES:
NOTE: For extended sense codes: Sense pin pair value of 0 means those pins should be tied together (as opposed to grounding 10, 7, or 4 to pin 11); value of 1, do not connect. DON'T wire any of these pins to ground.
| Display | Sense pins
4-10 10-7 7-4 | Hor x Vert
Pixels | Bandwidth
(MHz) | Refresh
(Hz) | Scan
(KHz) |
| 16-inch Color, such as E-Machines | 0 1 1 | 832 x 624 | 57.2832 | 75 | 49.7 |
|
| PAL (1) |
| PAL Option 1 | 0 0 0 | underscan
640 x 480 | 14.75 | 50 | 15.625 |
overscan
768 x 576 | 14.75 | 50 | 15.625 |
| PAL Option 2 (2) | 1 1 0 | underscan
640 x 480 | 14.75 | 50 | 15.625 |
overscan
768 x 576 | 14.75 | 50 | 15.625 |
|
| VGA | 1 0 1 | 640 x 480 | 25.175 | 59.95 | 31.47 |
| Super VGA (3) | 1 0 1 | 800 x 600 | 36 | 56 | 35.16 |
|
| 19" Color | 1 1 0 | 1024 x 768 | 80 | 75 | 60.24 |
| No external monitor (video halted) | 1 1 1 | |
NOTES:
1. PAL has two wiring options, using the extended sense pin configuration. To produce a color PAL signal, an RGB-to-PAL converter is required.
2. This sense code also requires a diode between sense pins 10 and 7, with anode towards pin 7, cathode towards pin 10.
3. To enable Super VGA, after configuring and connecting the monitor for VGA, open the monitor's control panel and select Options. Choose Super VGA from the dialog and restart your system.
4. The Macintosh Quadra 700 and 900 support PAL Option 1 at up to 8 bpp.
5. The Macintosh Centris 610, 650, and Quadra 800 support PAL Option 1 at up to 16 bpp.
6. The Macintosh Quadra 950 supports PAL Option 1 up to millions of colors.
MACINTOSH QUADRA AND CENTRIS VIDEO PINOUTS:
| Pin | Signal | Description |
| 1 | RED.GND | Red Video Ground |
| 2 | RED.VID | Red Video |
| 3 | CYSNC~ | Composite Sync |
| 4 | MON.ID1 | Monitor ID, Bit 1 (also known as SENSE0) |
| 5 | GRN.VID | Green Video |
| 6 | GRN.GND | Green Video Ground |
| 7 | MON.ID2 | Monitor ID, Bit 2 (also known as SENSE1) |
| 8 | NC | No Connection |
| 9 | BLU.VID | Blue Video |
| 10 | MON.ID3 | Monitor ID, Bit 3 (also known as SENSE2) |
| 11 | C&VSYNC.GND | CSYNC & VSYNC Ground |
| 12 | VSYNC~ | Vertical Sync |
| 13 | BLU.GND | Blue Video Ground |
| 14 | HSYNC.GND | HSYNC Ground |
| 15 | HSYNC~ | Horizontal Sync |
| Shell | CHASSIS.GND | Chassis Ground |
If your monitor is a VGA type, try the following cable pinouts.
A cable wired as follows may allow many different brands of VGA monitors to work on a Macintosh Quadra. We advise you to test the monitor on a Macintosh Quadra prior to purchase to see if it meets your expectations.
Cable Pinouts:
Macintosh Video
DB-15 | Signal | VGA Connector |
| 2 | Red Video | 1 |
| 1 | Red Ground | 6 |
| 9 | Blue Video | 3 |
| 13 | Blue Ground | 8 |
| 5 | Green Video | 2 |
| 6 | Green Ground | 7 |
| 15 | Hsync | 13 |
| 12 | Vsync | 14 |
| 14 | Sync Ground | 10 |
| 10 | Connect 10 and 7 so the sense pin ID will equal VGA. |
| 7 |
There are a few issues to keep in mind with VGA monitors.
* VGA monitors will vary depending on the vendor. Check with the vendor about Macintosh Centris and Quadra compatibility before buying, or better yet, actually try the monitor with a Centris or Quadra to see if it works and if the quality is acceptable.
* Vendors have different image quality specifications. There may be significant differences between Apple monitors and the wide range of VGA monitors. Do a side-by-side comparison of the monitors you are considering before buying.
* Many third party cable vendors have off-the-shelf cables that should work.
MACINTOSH QUADRA TO NTSC VIDEO CABLE:
Most NTSC devices use a RCA-type phono-connector and the following diagram uses that as a reference point. A cable wired as follows may allow many different brands of NTSC monitors to work on a Macintosh Centris or Quadra. We advise you to test the monitor on one of these machines prior to purchase to see if it meets your expectations.
Adjust the phono-connector side to whatever type of connector is used (RCA, BNC, etc.). "Tip" is the pin in the center of the connector (the signal); the sleeve is the flange around the outer edges of the connector (the chassis ground).
MACINTOSH QUADRA TO NTSC VIDEO CABLE EXAMPLE:
| Card Connector | RCA-Type Phono-Connector |
| 4 MON.ID1 (sense0) - - - -| |
| 7 MON.ID2 (sense1) - - - -| |
| 11 C&VSYNC.GND - - - - - - | |
| 5 GRN.VID -----------------> | Tip (signal) |
| Shell CHASSIS.GND --------------> | Sleeve (ground) |
Note: By grounding pin 4 and pin 7 to pin 11, the Macintosh Centris and Quadra CPUs are told that an interlaced (NTSC) monitor is attached. The actual black and white video signal is on pin 5 and connects to the center (Tip) of the phono-plug. The shell of the card connector connects to the sleeve of the phono-plug.
To acquire a color NTSC signal from a Quadra (or any Apple Macintosh display card), an RGB-to-NTSC converter is required, such as those available from RasterOps, Truevision, and Computer Friends. We do not have the cable requirements for any of these interface devices.