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I have a Mini DisplayPort to DVI adapter which I use to connect my MacBook to a screen that has DVI input. I also have a screen with VGA only input which I want to be able to use, so instead of buying yet another expensive Apple adapter (the Mini DisplayPort to VGA), I just got a cheap DVI to VGA, so I can do Mini DisplayPort -> DVI -> VGA. It doesn't seem to work though. The screen just says "no connection".

Does anyone know if this is actually supposed to work (and my DVI -> VGA is just broken), or is this simply not supported and I need to get the expensive Apple Mini DisplayPort to VGA?

Thanks!

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I don't know for certain, but this is my guess.

DisplayPort is digital. VGA is analogue. DVI (DVI-I) supports both.

The DisplayPort to DVI adapter is only using the digital part of the DVI (DIV-D) standard. The DVI to VGA adapter used the analogue part (DVI-A).

The DisplayPort to VGA adapter probably does a complete conversion, hence being more expensive. It isn't just an electrical connection, but involved some processing too.

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This is my worry too. Though I think the price of the Mini DisplayPort to VGA is high just because it's Apple. Mini DisplayPort to DVI was also expensive. :) – ibz May 22 '10 at 11:15
The Displayport -> VGA adapter doesn't have any processing, just wiring. The Displayport standard supports many different signals, one of them being the analog VGA. Others include (Single-Link) DVI and HDMI including DHCP, LVDS and of course the proprietary (and specification-wise superior) Displayport standard. – dtech Dec 2 '11 at 17:14
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