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DisplayPort to HDMI adapters generally cost about 7 dollars. But if you want to go the other way round, you will need to dive a whole lot deeper into your pockets. The reason? An HDMI to DisplayPort conversion always requires an active instead of a passive adapter.

The tippy technology that allows the use of a simple passive adapter, is called HD DisplayPort Dual-Mode (or DP++). Although this is an optional feature and not part of the actual standard, it is available on most consumer devices’ video cards. You might find the DP++ logo on the device, but because it is so widespread most modern consumer products don’t mention the logo anymore.

The theory of DP++ is actually quite simple: when the device detects an MI adapter attached to it, the graphics card or GPU (Graphical Processing Unit) will automatically make a translation and send HDMI TMDS signals via the video output. The pins of the DisplayPort connector are then mapped onto the HDMI pins, making the transition very simple. The system is completely plug and play, handles both video and audio, and does not need any driver to work. You even don't really need a special adapter anymore, because there are DisplayPort to HDMI cables available on the market. There is normally no loss in quality when using such a dp to hdmi cable. Note however that this simple transition only applies to single-link DVI signals, so up to HD resolution. Furthermore, when you want to connect multiple DVI or HDMI monitors to a DisplayPort output, you will need an active adapter or splitter as well. Many graphics cards can’t support DP++ output to multiple monitors.

Does this easy conversion with DP++ mean that every screen or projector should just have an HDMI interface? No, it does not, because it’s always better to connect devices which use the same protocol. First of all, the voltage level-shifter circuit poses a restriction on the speed of the adapter. Although new adapters become available whenever an increase in bandwidth is introduced, you always need to buy the appropriate model. Furthermore, this only applies to Single-link DVI connections. Because a Dual-link DVI signal needs 25 pins, it cannot be transmitted from a DisplayPort connector using a passive adapter. You always need an active adapter converter to make this translation.

Note also that DP++ is not available on DisplayPort Alternate Mode over USB-C (as is used on many current compact devices like smartphones and notebooks). So if you use USB-C you will always need an active adapter to connect to an HDMI display.