[geeks] Not all cables are created equal (DVI)

[Francois Dion]

Just wanted to mention, if you buy an LCD monitor and you run
>1280x1024 at 60hz and you notice that you can run at that resolution
with the analog (vga) input but cannot run anything higher than
1280x1024 in digital mode, you are a victim of a cheap manufacturer.

Viz, I got a Samsung SyncMaster 204B, very happy with it, does
1600x1200. It came with a DVI cable, strange because Samsung doesn't
ship one according to their web site. This however was bought from
Dell (dont ask), so I'm assuming they added their own cable. I just
replaced my ATI with a Quadro FX 550 (you need an Nvidia card to get
accelerated OpenGL in Solaris x86/x64) which has 2 DVI ports. So I
used the cable that shipped with the monitor to connect to the video
card, but it kept forcing 1280x1024, stating the monitor couldn't do
higher, which is not true.

In the meantime I had already ordered a longer DVI cable, because the
bundled cable was too short. I was regretting having put more money
into something that wouldn't work for me. Well, upon receiving the new
cable, the issue became obvious. The cable that shipped with the
monitor is a "single link" while the new cable (I asked for a 15ft
DVI-D capable of 1600x1200) is a "dual link" (see the illustration at
http://en.wikipedia.org/wiki/DVI ).

I had the same problem on a 1440 wide resolution lcd monitor and this
also cured that problem. I tought a spec was a spec... imagine cat5e
cable incapable of doing anything faster than 100mbps....

Now on the wikipedia page (and a bunch of other places) they state:

Example display modes (single link):
    * UXGA (1600 W 1200) @ 60 Hz with GTF blanking (161 MHz)
    * WUXGA (1920 W 1200) @ 60 Hz (154 MHz)
    * SXGA (1280 W 1024) @ 85 Hz with GTF blanking (159 MHz)

Yet the Quadro FX sense reports that the 6ft long single link cable
couldn't get to UXGA resolution (for example). The 15ft long dual link
had no problem, but it is supposed to be capable of (according to
wikipedia again):

HDTV (1920 W 1080) @ 85 Hz with GTF blanking (2W126 MHz)
WQXGA (2560 W 1600)@ 60 Hz with GTF blanking (2x174 MHz) (30" LCD
Dell, Apple, Samsung)

However the DVI-D dual link I received ("QVS digital dvi premium
cable") only supports 1600x1200.

So, clearly, in the DVI-D world, single vs. dual link is not the only
defining factor of what resolution you'll be able to do.

Francois