External monitor cable for Performa 5200

[noglin]

I want to record the screen from my Macintosh Performa 5200. For that I need the mirror-cable. I've been able to video capture my PowerBook 5300 with a chain of PB5300 -> MacDB -> VGA -> HDMI -> USB HDMI Capture Card -> MacBook Air, and planning to do the same (maybe there are better ways?).

I have two questions on this one. First, reading the developer notes: it is a cable + a video buffer. Would it have any performance impact or limitations? (

I found the cable on ebay from US, but the import processing fee they charge in Spain will make it not affordable (will be almost better to get a 6200 in Europe and record from the main screen of that one instead).

So I'm wondering if any other computer used this same cable? (I first thought the 6200 perhaps had it for its main video output, but seems not).


Extract from developer notes:

The Power Macintosh 5200 uses a feature, called video display mirror output, to make
the video information on its built-in monitor available to an external monitor. This
means that the information displayed on an external monitor is a mirror image of that
displayed on the built-in monitor. This feature is implemented by plugging an optional
video buffer board into the 22-pin Video Mirror connector on the main logic board

Image of the cable from ebay:

 

[Byrd]

I think that adapter is compatible with AIO 575, 580 and 5x00 and 6x00 machines (including the TAM) - they all have this slot. They are quite useful adapters to have in some Macs, especially to plug in to projectors and CRT/LCD with no loss in quality

 

[noglin]

Thanks! Do you know if these are considered rare? I would prefer to wait and see if I can get one within EU to avoid the customs processing fees, but might just need to bite the bullet.

 

[demik]

They are kinda rare, mostly used in classrooms back then. Wouldn't be too hard to reproduce tho if someone can draw the schematics

 

[François]

Wouldn't be too hard to reproduce tho if someone can draw the schematics

Providing someone can identify the chips:

The small one is a quad video amp, but I was unable to find the big one (I only did a quick search, I’m not a specialist in chip identification)

 

[NJRoadfan]

It is likely a standard buffered analog video output circuit of some sort.

 

[Daniël]

The small one is a quad video amp, but I was unable to find the big one (I only did a quick search, I’m not a specialist in chip identification)

It's a TI SN74F240, "Octal Buffers/Drivers With 3-State Outputs". If I had to make a guess, it might have to do with the monitor ID system on the DB-15 connector.

 

[noglin]

Thanks everyone! I actually managed to find one by chance on marktplaats, boxed new. Once I have it home I'll post picture here as well in case it might be useful if anyone would pursue building this.

 

[cheesestraws]

it is a cable + a video buffer. Would it have any performance impact or limitations?

since people have only implicitly answered this question, perhaps an explicit answer will be useful (maybe to you, maybe to some future person who finds this thread):

the buffering in question here is buffering in the electronics sense of the word, not in the computing sense of the word. It is not a buffer like a framebuffer, it is a regeneration of the video signal so that it and the internal display can each have a full whack of transmission power, rather than having half the power each. It won't result in any added latency or performance disadvantages (at least, unless Apple managed to cock up the implementation rather more than they usually do). Nothing is being stored, there's no memory or anything.