mini-DVI to DVI adapters and analog signals

Mini-DVI is an Apple-specific port they use on products (such as their 12″ and 13″ laptops) where a full-size DVI port would take up too much space. [update: The 13″ MacBook Air, announced today, would seem to use micro-DVI, not mini-DVI.]

It seems obvious that it would be possible to build a mini-DVI to DVI-I adapter that carries both digital and analog signals. After all, Apple sells adapters that convert from mini-DVI to both DVI and VGA, so both analog and digital signals must be available in the mini-DVI port.

Apple says of mini-DVI, “The computer detects which adapter is present by reading its EDID (Extended Display Identification Data) via DDC. The EDID for video is in the adapter; the EDID for VGA and DVI are in the display.” But I think we can presume (can we?) that for both DVI and VGA that the DDC/EDID conversation between the mini-DVI port and the monitor is passed straight through the adapter unadulterated. It’s only the adapter providing S-video and composite video ports that plays DDC/EDID tricks.

So the only reason for a miniDVI-to-DVI adapter not to pass through the analog signals is to save a few conductors in the cable. Yet it seems both games in town have in fact done this.

It’s obvious Apple does it, since the female DVI connector on their adapter lacks sockets for the analog pins. [See this image to confirm that it has a DVI-D socket connector that won’t physically accept the analog pins (above and below the blade pin) of common DVI-to-VGA cables such as this one.]

The only other manufacturer of mini-DVI to DVI adapters I can find is Dynex. Dynex’s mini-DVI to DVI cable has a female DVI-I connector, so analog cables will physically fit, but this thread confirms that the analog signals aren’t passed. The DDC/EDID data gets through, but either there aren’t conductors for the analog signals or possibly the RAMDAC that would be generating the analog signals is somehow getting shut down.

[edit: I found another adapter at Monoprice but it also has a DVI-D connector. Monoprice also sells a mini-DVI to HMDI adapter.]

It would be nice to be able to carry around a single mini-DVI adapter that could provide both digital and analog signals. Comments?


5 thoughts on “mini-DVI to DVI adapters and analog signals

  1. Albany Lawyer Warren Redlich April 1, 2008 / 10:34am

    This is frustrating. I have two Macs I want to connect to big screen TVs through the TV’s HDMI connection: a new MacBook and a previous generation 24″ iMac.

    I think both Macs use mini-DVI. So how do I connect them? First I guess I use a mini-DVI to DVI adapter. Then a DVI to HDMI cable? [Yes, that should work. -ed.] I might have to visit the Apple Store, which for me is reasonably close.

    The wireless keyboard and mouse were easy to set up. The connections to the HDTVs should be easier too.

    Another annoyance is that I have an older iBook which used a different form of DVI output. I hooked that up to a VGA cable with an adapter, but the DVI adapter is different and I want to use the full screen of the HDTV.

    So many cables and adapters, so little time. 🙂

  2. anagolg June 24, 2010 / 11:29am

    love the typo

    hate how apple always changes their non-standard cables in every hardware revision

    not to mention i had to get the mini-dvi to whatever adapter to plug into a separate HDMI adapter. now for vga i have to get another dongle which i am irked.

    if they were smart they could make some iMonitor dongle that interfaces with several output video types and then the input could just be the same raw output of their choosing. just stick with it.

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