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Apple Multiple Scan Software

With the release of the Apple 20" Multiple Scan Monitor, Apple became the third (that I know of) company to offer monitor resolution switching on the fly. The other contenders, NEC with their DPI-On-The-Fly software and Radius with their Soft Precision Color software, offer similar features.

The new Apple Multiple Scan Software that accompanies the Apple 20" Multi-Scan allows you to switch between most of the Centris, Quadra, and Power Mac video resolutions. For example, the Quadra can switch between 640 x 480, 832 x 624, 1024 x 768, and 1152 x 870 resolutions without restarting the Mac or changing adapters. Along with resolution switching, a few long-awaited features have come to the Monitors control panel. With multiple monitors, you can now move the menu bar from monitor to monitor without restarting your Mac. Rearranging the positions of multiple monitors also takes effect immediately. These two features should work with any multi-monitor setup.

For this magic to take place on your Centris, Quadra, or Power Mac, you need an Apple 17" or 20" Multi-Scan monitor. Or do you?

I can’t help but tinker when Apple releases anything new. The new 20" was no exception. After a few minutes with a multi-meter and a handful of parts, I found out that nothing more than a diode and a couple of DB-15 connectors allows any multi-scan monitor to perform the same feats of magic. Be aware that all previous Apple monitors were fixed resolution, and will NOT benefit from this hack, it ONLY works with multi-scan monitors (also referred to as multisync), such as the Sony 1730. So, if you are handy with a soldering iron and have $5 to cover the parts cost, you’re good to go on the Magical Multiple Resolution Ride! (Please, no food or beverages.)

To begin, here is the list of parts:

  • 1 DB-15 Male solder pot connector. (JDR Part# DB15P)
  • 1 DB-15 Female solder pot connector. (JDR Part# DB15S)
  • 2 DB-15 Hoods to cover your handiwork. (JDR Part# MPHOOD15)
  • 1 1N914 or 1N4148 diode (RS Part# 276-1122, JDR Part# 1N4148)
  • Apple Multiple Scan Software installer disk. (You get to find this one)
  • Wire, solder, and 30 minutes. (That’s tinkerer time, it never counts)

The adapter can be wired up with the D connectors back to back with only a half inch of solid wire between connectors, no hoods, with electrical tape wrapped around the exposed wires for insulation. Or you can do as I have done, and make the adapter a short pigtail with 4-6" of stranded wire between connectors. The pigtail looks neater, and avoids stress on your Mac’s video connector from a chain of adapters poking straight back. Feel free to substitute crimp style D connectors if you have tools to assemble them.

If your multi-scan monitor has a VGA style connector (3 rows of 5 pins), see the second wiring diagram and part substitution. Or if you prefer, you can plug your existing Mac-to-VGA adapter into the back of this adapter.

Wire the adapter thusly: (NC = No Connection)

            DB-15 Male               DB-15 Female
            ----------               ------------
                 2------ Red  Video ------2
                 1------ Red Ground ------1
                 5----- Green  Video -----5
                 6----- Green Ground -----6
                 9------ Blue Video ------9
                13----- Blue  Ground -----13
                 3---- Composite Sync ----3
                12-------- V Sync --------12
            |---11--- C,V Sync  Ground ---11
            |   15-------- H Sync --------15
            |   14---- H Sync  Ground ----14
            |    8------------------------8
            |----4                    NC--4
                 7--|<--|             NC--7
                10------|             NC--10

In the above diagram, pin 4 on the male side is shorted to pin 11 (ground). Pins 7 and 10 can be configured in two ways: If your monitor only supports resolutions up to 1024 x 768 at 75 Hz (such as the Sony 1304, 1430, 1604, or 1730), install the diode with the striped end soldered to pin 10 and the other end to pin 7. If your monitor supports all resolutions up to 1152 x 870 at 75 Hz (such as the non-Trinitron Supermatch 17), install the diode with the striped end to pin 7 and the other end to pin 10. This is critical, as it prevents a user from selecting a resolution that the monitor cannot display. If you are unsure, go with the 1024 x 768 diode installation.

Notice that pins 4, 7, and 10 are not passed through to anything on the female side. These are the ID pins that tell the computer what monitor is connected. If they were passed through this adapter, it is possible the cable or monitor attached to the female side may short additional ID pins to ground, defeating the monitor ID we have set.

If you are familiar with twisted pair wiring, you might use it for the Red, Blue, and Green signal/ground pairs to help eliminate possible interference. If you’re really RFI crazy, 75 ohm mini-coax would be primo. You may also wish to solder a wire from shell to shell for improved grounding.

With the hoods on and a final test with your meter, attach the male end to the back of your Mac, attach your multi-scan monitor to the female end and power up. Without the Apple Multiple Scan Software installed, the Mac should see the monitor as a 640 x 480 display. After installing the software, open the Monitors control panel and click on the Options button. You should be able to select between resolutions. As soon as the Options dialog closes, your monitor should blink out and come back at the selected resolution. If for some reason your monitor can’t display the selected resolution, restart your computer with your original cables and adapters. It will revert to a fixed frequency setting.

If you want to make a VGA-style adapter, here is the pinout. Substitute a HD-15 Female for the DB-15 Female; also you will need a DB-9 hood to cover the smaller HD-15 connector.

Wire the VGA adapter thusly: (NC = No Connection)

            DB-15 Male               HD-15 Female
            ----------               ------------
                 2------ Red  Video ------1
                 1------ Red Ground ------6
                 5----- Green  Video -----2
                 6----- Green Ground -----7
                 9------ Blue Video ------3
                13----- Blue  Ground -----8
                12-------- V Sync --------14
            |   15-------- H Sync --------13
            |   14----- Sync  Ground -----10
            |    3-- NC              NC --4
            |    8-- NC              NC --5
            |----4                   NC --9
                 7--|<--|            NC --11
                10------|            NC --12

Good luck, and happy syncing!

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