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Macintosh Portable Video Adapter
- Thread starter LaPorta
- Start date
There was a thread some months ago about this. As I recall the TL;DR is that the output port is basically just a paralleled copy of the LCD drive lines. I don't think anyone has succeeded in unearthing the datasheet for the Portable's panel, which would help a lot with trying to build an adapter, but you could probably figure out enough to do it with the help of a good oscilloscope.
How difficult the actual converter would be depends on what frequency it runs at and how many fields the panel is broken into. My guess is you'll need a dual-ported video buffer (32k will do) to paper over all the differences.
How difficult the actual converter would be depends on what frequency it runs at and how many fields the panel is broken into. My guess is you'll need a dual-ported video buffer (32k will do) to paper over all the differences.
Not much information online:
http://www.google.fr/url?url=http://archive.compgeke.com/PDF/Apple/product-data/displays/macintosh-portable-video-adapter-8909.pdf&rct=j&q=&esrc=s&sa=U&ved=0ahUKEwiEloH1hvDeAhUjy4UKHT39BK4QFggyMAg&usg=AOvVaw2mfN5vWJ8hV9VwsAoeety3
Was probably elusive
http://www.google.fr/url?url=http://archive.compgeke.com/PDF/Apple/product-data/displays/macintosh-portable-video-adapter-8909.pdf&rct=j&q=&esrc=s&sa=U&ved=0ahUKEwiEloH1hvDeAhUjy4UKHT39BK4QFggyMAg&usg=AOvVaw2mfN5vWJ8hV9VwsAoeety3
Was probably elusive
My impression was they never actually released an adapter for the port. Not in a position to check but my recollection is that there's an Apple KB article addressing this that recommends SCSI graphics adapters as a workaround. (There may also have been a really rare video card that went in the internal slot?)
So far as I can see in the KB from Apple:
https://support.apple.com/kb/TA45501?locale=en_US
This line is the most interesting: "Sayett Technology's DataShow, an overhead viewplate that connectsdirectly to the Portable's Video Out port"
Apparently this device actually did work with the video port. If anyone knows where to find one is another story...
https://support.apple.com/kb/TA45501?locale=en_US
This line is the most interesting: "Sayett Technology's DataShow, an overhead viewplate that connectsdirectly to the Portable's Video Out port"
Apparently this device actually did work with the video port. If anyone knows where to find one is another story...
There is a Datashow Premiere on eBay, not sure if it's a model that supports Macintosh Portable. Maybe someone could tell by the cables?
I took a look at the thread that Gorgonops referenced. It looks like that guy was trying hard to do some crazy mods to get a 1080 LCD packed into the Portable. All I'm attempting to do is get some sort of VGA-style output, but it looks like that would be really involved. I am lucky that before I knew all of this, I didn't ruin the LCD monitor that I have by hooking it up accidentally 
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I'd be willing to bet a shiny new nickel that device was based on an LCD that was compatible, or close to it, with the built in one.
The title of the KB article that I vaguely remembered, linked above and now here is "Macintosh Portable: External Video Adapter Canceled (6/96)"
So, yes, it was cancelled, apparently. Because of the inherent complexity of what it needs to do it would have been painfully expensive for what it was capable of, which probably helped motivate the final decision.
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I have no doubt you are correct. Something like that would be perfect for an LCD that would be used with an overhead projector.
Broadly speaking I think it would be relatively easy to make this adapter if you had the specs for the LCD (or the tools to reverse engineer which of several likely logical geometries it's laid out in) and had some skill in programming FPGAs. As noted, the simplest approach would be to set up a dual-ported 32kb framebuffer large enough to hold a monochrome 640x400 grid of pixels that has glue that emulates the LCD interface on the input side and an output stage that spits out a VGA compatible signal. Sample code for doing the VGA part on an FPGA is readily available, you just need to work out how to handle the input data. Could probably build the whole thing using half a dozen components (figure a voltage regulator, a few input level shifters since the FPGA will probably be a 3.3v part, and some resistors for the VGA output), a little $20 FPGA dev board like this would be serious overkill for the job.
Building it with discrete components would be an ugly task, though.
Building it with discrete components would be an ugly task, though.
Reverse engineering something like the Radius TPD Video Card for the SE and reducing the layout to fit SMT chiplets and cannibalized custom Radius ICs onto the two sides of a Portable PDS card would be one approach. The slots are not the same pinout, but are signal compatible. Xpanse made a Chassis/Portable PDS card combo in with TWO SE PDS card slots.
Of course we haven't gotten that card working on a Multiscan Display quite yet. But that prospect doesn't seem like all that hard to do by comparison. Somebody else started that project thread and I jumped in with my card and the newly acquired SE/Radius16.
That would give you a two display desktop. Did the Portable ever do more than mirroring on that panel?
Of course we haven't gotten that card working on a Multiscan Display quite yet. But that prospect doesn't seem like all that hard to do by comparison. Somebody else started that project thread and I jumped in with my card and the newly acquired SE/Radius16.
That would give you a two display desktop. Did the Portable ever do more than mirroring on that panel?
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It is impossible for the Portable to do anything but mirroring on its integral port. The lines running to it are literally the same ones as those that run to the built-in panel.
That answers that, just checked your first reply and that info was in it, but wasn't clear at all. That video port was all but useless before first release. Repackaging an SE VidCard's components would then be only remotely viable option outside of developing an entirely new VidCard from scratch. A new design would be good for both Portable and SE, if not Plus and Classic as well.
I really wish I'd snagged that Video Card Prototype/Media/Development Documentation package that was listed on eBay. Couldn't have done anything with it myself, but it wouldn't have sunken into oblivion. Did anybody here or out there among the lurkers snatch it?
I really wish I'd snagged that Video Card Prototype/Media/Development Documentation package that was listed on eBay. Couldn't have done anything with it myself, but it wouldn't have sunken into oblivion. Did anybody here or out there among the lurkers snatch it?
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The portable works on an 8-bit parallel pixel input per pixel clock. Unfortunately I am not entirely sure how those pixels are arranged whether they are 8 next to each other, or 1 every other row, etc..
I have the pinouts of both displays, and the rear port.
From the limited studies I have done, there are 2 clock signals and a framing signal. Only 1 of the two clock signals is going to the external port, which is CL2. CL2 the pixel clock, and CL1 is the line sync (Horizontal Sync) signal.
My assumption of FLM being the framing signal is because it is also going into the MISC GLU which probably generates the VBI from the FLM signal.
FLM = First Line Marker, aka Vertical Sync.
Anyways, I havent hooked it up to a scope yet (really need a logic analyzer honestly) to figure out the sequence diagram to figure out how the 8 bits are mapped to the pixel areas. I am familiar with most 4-bit displays, and it goes vertical. D4 being the top pixel, D0 being the 4th pixel down from the top.
View attachment LCD Interface.pdf
I have the pinouts of both displays, and the rear port.
From the limited studies I have done, there are 2 clock signals and a framing signal. Only 1 of the two clock signals is going to the external port, which is CL2. CL2 the pixel clock, and CL1 is the line sync (Horizontal Sync) signal.
My assumption of FLM being the framing signal is because it is also going into the MISC GLU which probably generates the VBI from the FLM signal.
FLM = First Line Marker, aka Vertical Sync.
Anyways, I havent hooked it up to a scope yet (really need a logic analyzer honestly) to figure out the sequence diagram to figure out how the 8 bits are mapped to the pixel areas. I am familiar with most 4-bit displays, and it goes vertical. D4 being the top pixel, D0 being the 4th pixel down from the top.
View attachment LCD Interface.pdf
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