Macintosh AV: NTSC Underscan with Multiple Scan Display

The Multiple Scan Display software doesn't show the 512 x 384 (NTSC underscan) resolution in the Monitors control panel, because the Multiple Scan Displays do not directly support that resolution. The monitor's software patches the Macintosh AV video ROM routines to enable the computers to do the dynamic resolution switching.

Here are the steps required to get the NTSC underscan resolution of 512 x 384:

Macintosh Quadra AV Series

1. Open the Monitors control panel.

2. If the Multiple Scan display is not set to 640 x 480:
- Click the "Options..." button.
- Change to the "Macintosh Hi-Res Display" resolution and click OK.

3. Hold down the Option key on the keyboard and click the "Options..." button.

4. Change to the 512 x 384 resolution and click OK.

5. Click OK to confirm that the smaller image appeared.

6. Change to "Display Video on Television" and click OK.

7. Click the "Switch" button to display the image on the Television.

Note: The additional resolution options are available when the extensions are off because the Multiple Scan Display software does not get loaded, so the video ROM is not patched.

Power Macintosh AV Series

1. Open the Monitors control panel. Click the "Options..." button.

2. Choose "Display Video on Television" button and the "Upon Restart Display Video on Television" button. Click "OK".

3. Click "Rearrange on Restart" radio button and close the Monitors control panel.

4. Restart. Video will display on TV in 640 x 480 mode.

5. Open the Monitors control panel. Click "Options...".

6. Choose the "512 x 384" setting. Choose "Upon Restart Display Video on Television" button. Click "OK". Click the "Rearrange on close" button and close the Monitors control panel.