68kMLA Classic Interface
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| NTSC Monitor | |
| Posted by: luRaichu on 2024-04-08 12:31:35 I noticed the Macintosh seems to have provisions for NTSC/PAL composite output, according to the monitor sense codes documentation.  Has anyone successfully coaxed a composite signal out of the Mac video port? | |
| Posted by: NJRoadfan on 2024-04-08 13:52:43 Composite color would require the card have a NTSC encoder on it. RGB would be doable though. If the card can output 15.75khz video, those sense pins would be used with a monitor like the IIgs AppleColor RGB or the Commodore 1084. | |
| Posted by: cheesestraws on 2024-04-08 14:23:27 Note that just because a sense code is specified for those monitor types doesn't mean that anything was ever actually released to drive them: it just meant that, at some point, they thought they might release something to drive them. That said, that weird broadcast video card with the name I can't remember (this is wildly unhelpful; it's got a black PCB and looks really cool, someone here has one and they turn up on buyee relatively often and it's really annoying not even remembering the manufacturer) does broadcast resolutions, and maybe that will use those sense codes? | |
| Posted by: halkyardo on 2024-04-08 14:24:31 I don't believe any Macs were able to output colour composite video from the 15-pin connector, except maybe some specialised video cards (the AV Macs are a different story). The video output is still RGB in those modes, just with resolution and timings suitable for NTSC or PAL. You CAN however get greyscale composite video from some video cards by setting an NTSC or PAL sense code and using the green channel as the video output. I've done this with an E-Machines Futura SX card in my IIfx, and the RasterOps ColorBoard 264 card in my SE/30 will do it too. The picture quality is nothing to write home about, but it does work! | |
| Posted by: Phipli on 2024-04-08 14:43:59 So, I think I remember that it's only half the story. Several Apple video cards and built in video supported these modes, but required an external box in combination to archive it. | |
| Posted by: Phipli on 2024-04-08 14:46:33 Here is some info 🙂 
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| Posted by: luRaichu on 2024-04-08 16:24:28 Would this trick work on the LC? | |
Posted by: Phipli on 2024-04-08 16:26:41Would this trick work on the LC?Which trick? Regardless, I suspect the short answer is no 🙂 The LC is Low Cost - they cut out a load of video stuff. | |
| Posted by: finkmac on 2024-04-08 16:37:47 ++ @Phipli i know the Macintosh II Toby definitely supports this.. but you need a special cable. There was utility on macintosh garden (that I can't seem to find) that enables this mode. | |
| Posted by: joevt on 2024-04-08 16:44:02 One time, I connected an RGB NTSC CRT to my Power Mac 8600's built-in video output. I think it was a Commodore 1070 display and I had to modify the sync connection inside the display for separate sync. I wonder if an Apple IIGS display could be connected? I think that would require an adapter since some pins are not the same as Mac. You can connect a NTSC or PAL RGB virtual display to DingusPPC emulator. I need to push a commit to fix the issue where every second line is skipped and the frame rate is set to 30Hz instead of 60Hz. I had an LC. I think it was limited to 12", 13", and VGA displays. No interlaced displays. | |
| Posted by: finkmac on 2024-04-08 16:45:36 Found it. | |
| Posted by: NJRoadfan on 2024-04-08 18:27:58 Pin 5 is green video, which also carries sync. When running at NTSC rates = black and white composite video. The Apple IIgs monitor uses the same pinout as the Macintosh DB-15 and only accepts composite sync on pin 3. If you can force the Toby and other machines to 15.75khz RGB with composite sync, it should work fine with the IIgs monitor. | |
| Posted by: luRaichu on 2024-04-08 19:58:13 Okay, but what about the PowerBook 180? | |
| Posted by: halkyardo on 2024-04-08 20:36:58 That’s a good question. Its video output supports a number of different resolutions so having support for an interlaced display wouldn’t be beyond the bounds of possibility. I’d very much doubt if it could do colour composite output, but interlaced 60Hz RGB sounds pretty likely. You’ve piqued my curiosity though. I’ll dig out my 180c and some adapter cables tomorrow night and have a play around and see what it’ll do. | |
| Posted by: finkmac on 2024-04-08 21:27:12 PowerBook 160/180 Devnote Might be useful... | |
Posted by: luRaichu on 2024-04-09 06:30:30 These are the officially supported monitors. Nothing points to interlaced output, though. | |
| Posted by: halkyardo on 2024-04-09 06:39:58 The 15.6672 MHz dot clock for 512x384 would also be plausible for an underscanned 640x480i mode, so while it not being listed certainly doesn't bode well, it still wouldn't be beyond the bounds of possibility that it could exist as an unsupported mode. Stranger things have happened. If I can find some space to set up my 180c and a monitor tonight, I'll experiment and see what it'll do. | |
| Posted by: Phipli on 2024-04-09 06:44:14 Have you considered one of these, or the apple branded equivalent? or 
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| Posted by: halkyardo on 2024-04-09 15:45:00 Just did an experiment with my 180c, and it does *not* seem to recognise a monitor attached with the NTSC Monitor sense code (100), nor PAL Encoder (extended sense 00-00-00) or PAL Monitor (extended sense 11-00-00). So that seems to put paid to that idea, sorry 🙁 | |
| Posted by: NJRoadfan on 2024-04-15 13:55:55 Action Retro's latest video shows a SuperMac SCSI video adapter that can run in 15.75khz mode. Its mostly for the composite video port, but it clearly outputs RGB at the same timings. | |
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