Compare DVI‑I and DVI‑D | Important differences

DVI is one of the most com­mon inter­faces in the mid-price seg­ment for con­nect­ing a com­put­er and a mon­i­tor. It is he who can be found on bud­get and inex­pen­sive video cards, as well as on office and home dis­plays with res­o­lu­tions up to Full HD inclu­sive and refresh rates up to 60 Hz.

DVI itself is one of the first dig­i­tal video trans­mis­sion stan­dards. Of course, even before him they tried to some­how aban­don the ana­log meth­ods of com­mu­ni­ca­tion, which have an extreme­ly low band­width. But DVI is the most wide­ly used.

And this pro­to­col itself exists in three vari­a­tions — DVI‑A, DVI‑D and DVI‑I. They dif­fer, among oth­er things, in the num­ber of con­tacts involved in sig­nal trans­mis­sion. Let’s fig­ure out what are the main dif­fer­ences and sim­i­lar­i­ties between DVI‑I and DVI‑D, as well as how Sin­gle Link dif­fers from Dual Link.

How DVI works

Despite the fact that DVI is, in prin­ci­ple, a dig­i­tal inter­face, which is reflect­ed even in the name, which stands for “Dig­i­tal Visu­al Inter­face”, when devel­op­ing it, the cre­ators decid­ed to achieve com­pat­i­bil­i­ty with old mon­i­tors. And for these pur­pos­es, sup­port for ana­log data trans­fer was added to the bus.

The ana­log data pins are to the right of the 24-pin bus on the dig­i­tal por­tion of the pack­age. These are the ones with a “long” “ground” and 4 addi­tion­al con­nec­tors above and below it. On this bus, infor­ma­tion about the loca­tion of red, blue and green pix­els (RGB mod­el) is trans­mit­ted in ana­log form.

The 24-pin main bus is need­ed for dig­i­tal data trans­fer. And, depend­ing on the type of DVI, it can phys­i­cal­ly con­sist of a dif­fer­ent num­ber of con­nec­tors.

So, DVI‑I SL and DVI‑D SL means con­nect­ing 18 pins. And DL — all 24. The DVI‑A ana­log pro­to­col uses main­ly “ground” con­tacts — 12 con­nec­tors from the main bus.

After con­nect­ing the mon­i­tor, the moth­er­board deter­mines which stan­dard is com­pat­i­ble with this screen. Then the clock fre­quen­cy, res­o­lu­tion and oth­er oper­at­ing para­me­ters are adjust­ed. What is very impor­tant, the band­width of the DVI inter­face depends on the length of the cable. The same mon­i­tor con­nect­ed with 2m or 10m wires will have dif­fer­ent res­o­lu­tion and refresh rate.

It is also worth not­ing that there are two ways to con­nect mon­i­tors via the DVI con­nec­tor — Sin­gle Link and Dual Link.

The fact is that the con­nec­tor is equipped with duplex con­tacts that dupli­cate each oth­er. So, he has two red pairs, two blue pairs, two green pairs. Each pair is, in fact, “plus” and “minus”.

If the mon­i­tor receives data from only one trio of pairs, this is called Sin­gle Link (SL). If from two, then already Dual Link (DL).

DL mode dou­bles the bus band­width. And this is nec­es­sary to achieve two goals — either dou­ble the max­i­mum sup­port­ed res­o­lu­tion, or also dou­ble the refresh rate.

The fact is that the DVI pro­to­col in SL mode works with mon­i­tors of a rather low res­o­lu­tion. The max­i­mum sup­port­ed is 1920×1080 pix­els (Full HD). In SL mode, it can be increased many times — for exam­ple, up to 2560 × 1600 pix­els.

DVI‑D interface

DVI‑D (Dig­i­tal Visu­al Inter­face — Dig­i­tal) is an exclu­sive­ly dig­i­tal video data trans­mis­sion inter­face. It is com­mon­ly used in mod­ern mon­i­tors and graph­ics cards due to its low cost and ease of pro­duc­tion. Also, devel­op­ers do not need to achieve com­pat­i­bil­i­ty with lega­cy tech­nolo­gies.

DVI‑D can oper­ate in two modes — Sin­gle Link and Dual Link. In the first case, the max­i­mum clock fre­quen­cy is 85 Hz on small (up to SXGA inclu­sive) screens, in the sec­ond — 120 Hz on screens up to WUXGA, includ­ing Full HD.

DVI interface

DVI‑I (Dig­i­tal Visu­al Inter­face — Inte­grat­ed) is a dig­i­tal-ana­log video sig­nal trans­mis­sion inter­face. It adapts itself accord­ing to the con­di­tions of use and can switch from dig­i­tal to ana­log trans­mis­sion.

Most often, video cards of the mid­dle price seg­ment are equipped with the DVI‑I stan­dard, and imme­di­ate­ly in the DL ver­sion. Thanks to it, they are able to trans­mit HD video or stream with an excel­lent frame rate to any con­nect­ed mon­i­tor or pro­jec­tor.

Because the ana­log and dig­i­tal pins are on oppo­site sides of the con­nec­tor, they have no effect on each oth­er. And the res­o­lu­tion and clock speed are the same as DVI‑D.

Differences and similarities between DVI‑I and DVI‑D

So, DVI‑D is an exclu­sive­ly dig­i­tal inter­face, and DVI‑I sup­ports the trans­mis­sion of both dig­i­tal and ana­log sig­nals. Essen­tial­ly, DVI‑D is part of DVI‑I.

Let’s com­pare both options and deter­mine which is bet­ter.

It is clear that the only dif­fer­ence between these two inter­faces is the pres­ence of con­tacts for trans­mit­ting an ana­log sig­nal.

Development of standards

How­ev­er, in mod­ern video cards (pro­duced after about 2013), this con­nec­tor is prac­ti­cal­ly not found. This is due to a fair­ly large num­ber of short­com­ings. Among them:

1. Increased sen­si­tiv­i­ty to exter­nal elec­tro­mag­net­ic fields, which can become a source of inter­fer­ence and noise;

2. Notice­able sig­nal loss with a long cable length (from 2 meters);

3. Poor com­pat­i­bil­i­ty with non-stan­dard for­mat screens (such as 32:9);

4. Inabil­i­ty (even in DL) to work at 4K res­o­lu­tion.

Because of all these short­com­ings, it began to be grad­u­al­ly aban­doned. More­over, in 2013 HDMI 2.0 was intro­duced, which brought sup­port for impres­sive­ly high res­o­lu­tions. And then Dis­play­Port came out, which has even more band­width and there­fore even sup­ports 8K mon­i­tors in iter­a­tion 1.4 — and can work on top of the USB Type‑C con­nec­tor, which is gen­er­al­ly amaz­ing.

New video trans­mis­sion stan­dards have proven to be more scal­able and per­for­mant than DVI. And that is why they began to refuse it. At the time of this writ­ing (April 2019), these con­nec­tors are extreme­ly rare, and DVI‑I is gen­er­al­ly only left in “muse­um” video cards.

There­fore, when assem­bling a new com­put­er, you should not chase cheap­ness and the manda­to­ry pres­ence of a DVI con­nec­tor. At the moment, there are many more pro­duc­tive stan­dards.