The DVI cable I had used for a long time proved to be inadequate, too. Although its connectors have all the pins necessary, the pins for the second DVI channel are just not connected. So, if you want to buy a new cable for your 30” monitor, make sure it does support Dual-Link DVI. Cable manufacturers usually write this on the packaging (if there is no explicit indication, the cable is mostly likely Single-Link DVI).
The picture above shows two DVI connectors: the right one can work with either one or two DVI channels while the left one can only work with one DVI channel. The missing group of pins for a second channel is marked with red. But as I’ve written above, the presence of a connector with a full set of pins does not guarantee that the whole cable supports Dual-Link DVI.
I’m not talking about analog connection here. On a 24” monitor its quality depends on the particular graphics card, cable and monitor, but you can’t achieve any quality at a resolution of 2560x1600. As a matter of fact, 30” monitors are not equipped with an analog connector at all.
It is simple with 1920x1200 monitors. They can work with Single-Link DVI, utilizing a trick called reduced blanking. In a CRT monitor (the DVI interface is universal and supports any monitor type if the monitor has an appropriate input) there are beam blanking intervals between the lines of one frame and between two adjacent frames. During this interval the beam is returned from the end of the previous line to the beginning of the next one or from the end of one frame to the beginning of the next one, and no data is transferred to the monitor during this interval. There is no electronic beam in LCD monitors and there is no need for the beam blanking. Thus, data can be transferred in a denser stream than onto a CRT monitor. That is why Single-Link DVI cannot support the resolution of 1920x1200 pixels on CRT monitors at a scan rate of 60MHz, but it does support the 1920x1200@60Hz display mode on LCD monitors. In this case you won’t need a graphics card with support of Dual-Link DVI and a Dual-Link DVI cable.
27” monitors come with an analog input, too, but its usefulness is questionable. Even with best graphics cards you’ll have to run the auto-adjustment manually each time you turn the monitor on at 1920x1200. In the worst case you won’t be able to achieve a sharp picture at all.
Quite a reasonable remark when discussing large monitors, why do you need this screen size? Among everything else, the answer helps draw another separating line between 27” and 30” monitors: the former have the same resolution as 24” models and display the same amount of information. That is why 27” monitors are mainly interesting for people who often watch movies on the PC. The screen can never be too large for that purpose while the resolution can even be 1920x1080 (HDTV movies with this resolution have appeared but recently).
However, there are a lot of applications where a large display resolution, i.e. the ability of the display to show a lot of information at once, would come in handy. I mean engineers (a complex schematic is often easier to work with when you can view it all rather than in parts), architects, and the printing industry (when the large resolution allows to have a whole broadside in full on the screen). It comes in handy when you have to work with a few documents simultaneously – you can place them on a large monitor next to each other without overlapping. In the latter case one 30” monitors can be replaced with a couple of 20-21” ones which are going to be cheaper, but splitting the workspace in two parts is going to be inconvenient for working with design drawings.
Thus, 27” and 30” models can be viewed as having strictly different applications. 27” monitors may be interesting for people who often watch movies on their PC and who need a large screen with a resolution sufficient for HDTV. As opposed to them, 30” models may make a good work monitor for people who process complex design drawings and schematics or have to work with multiple documents at once.