How to connect a DisplayPort output to a DVI monitor input via an adaptor, supporting Dual-Link DVI
QUESTION I have a DisplayPort KVM switch which I want to hook up to a 30in Dell monitor with a 2560 x 1600 display resolution. Unfortunately, this monitor has only a DVI input. I bought a DisplayPort to DVI adaptor which claimed to support Dual-Link mode, but when I plugged it in I couldn't achieve the full resolution of my monitor. Is it possible to connect DisplayPort to DVI in this way or could there be a problem using the adaptor.
HELPROOM ANSWER It is possible to connect a DisplayPort output to a DVI monitor input via an adaptor, but the vast majority of available adaptors don't support Dual-Link DVI – which means they will be limited in the maximum resolution they can display. This will often be somewhere around 1920 x 1200 pixels, which is fine for most monitors but not for large displays such as yours.
We've found that many such adaptors which claim to support Dual-Link DVI do indeed feature a Dual-Link connector, meaning you can physically plug in a Dual-Link DVI cable, but don't actually support Dual-Link mode at all. It looks like this is the case with your adaptor.
To properly support conversion between DisplayPort and Dual-Link DVI, the adaptor needs to be 'active' (i.e. contain some electronics) and will require an external power source to drive them. This is usually achieved by fitting a USB connector to the adaptor which can then draw power from a spare USB port on your PC.
Dual-Link DVI effectively uses two simultaneous lower-resolution DVI connections to transmit the high-resolution picture data, whereas DisplayPort uses a single high-bandwidth connection. The adaptor has to deal with converting the image data between these two formats rather than simply connecting wires to different-shaped connectors at either end of a cable.
These additional features make true Dual-Link adaptors considerably more expensive: Apple's version, for example, costs £70 and user reviews on store.apple.com have reported some reliability issues. Dell also makes an adaptor, the Bizlink XT625, which may be a better match for your particular monitor. You should be able to buy one for around £40.