1920x1200 DVI issues

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Jan 31, 2005
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I'm running a Dell 2405FPW over DVI at 1920x1200 and getting flickering on port 1 of a Geforce 6800 Ultra.

It occurs under certain conditions. For example, whilst viewing this forum against a busy windows wallpaper.
eg. using this as my wallpaper:
blue_back.gif


And viewing a lighter window against it produces this:
artifact.jpg

A closeup:
artifact_close.jpg


On port 2 the flickering disappears. Anyone else experienced this problem? or able to reproduce it?
 
I had that issue with my 2005fpw and 6800gt. it went away on its own. I'm not sure how though.
 
the 1'st dvi port uses the built in nvidia tmds transmitter and that aint very good, the 2'nd port uses an externel transmitter with better signal quality.

just use the 2'nd port if you have problems with the 1'st
 
Spank said:
the 1'st dvi port uses the built in nvidia tmds transmitter and that aint very good, the 2'nd port uses an externel transmitter with better signal quality.

just use the 2'nd port if you have problems with the 1'st
Click to expand...

Yep, the flickering looks exactly like what I saw when trying to use my HP L2335 with a laptop when the built in graphics just wasn't up to the task.

As Spank says, Nvidia's integrated TMDS's are known for being right on the edge at 1920x1200x60. With their 2 DVI port cards, the second port uses a higher qaulity SiS TMDS, and so gives a cleaner picture. Hopefully you have a 2 DVI port card, and so have that option.

ATI's cards generally have slightly better integrated TMDS's, and don't show the same problem. When I was looking for a card at the start of the year I was about to get a 2 DVI port 6800 Ultra just for the second port, but ended up getting an ATI X850 XT PE as that's what was available at the time.

I've seen possts that indicate Nvidia's new 7800 series has a better TMDS, and so may not have this issue.
 
Thanks for the replies, I figured there must be a difference in the circuitry on the two ports. Wishful thinking on my part but it would have been nice to be able to use both DVI ports at the same time! :mad:

I hear the Quadro 4000 (6800 Ultra with two external TMDS DVI transmitters) doesn't have signal problems, so I'll keep any eye out for that on ebay.

I just find it rather bizarre that I can't use one of the DVI ports on a $400 video card without artifacting and need to fork out close to $1000 for the privilege.
 
This has been talked about before, but I am pretty sure this has to do with Dual Link DVI vs Single Link DVI.

I bet one DVI output on the card is Single Link, and the other is Dual Link. Each one supports different resolutions and refresh rates. Dual Link DVI would be the output to use for anything at 1920x1200@60Hz and above.
 
mike_j_johnson said:
This has been talked about before, but I am pretty sure this has to do with Dual Link DVI vs Single Link DVI.

I bet one DVI output on the card is Single Link, and the other is Dual Link. Each one supports different resolutions and refresh rates. Dual Link DVI would be the output to use for anything at 1920x1200@60Hz and above.
Click to expand...

This is possible but I don't think it's the case... unfortunately.
My little understanding about the subject and from things I have read shows that there really are very few Dual DVi ports on PC's... For this reason it's hard to get a graphics card that can correctly use Apples 30" which requires dual DVi (I read that on these forums which is where I'm getting my info from).
 
mike_j_johnson said:
This has been talked about before, but I am pretty sure this has to do with Dual Link DVI vs Single Link DVI.

I bet one DVI output on the card is Single Link, and the other is Dual Link. Each one supports different resolutions and refresh rates. Dual Link DVI would be the output to use for anything at 1920x1200@60Hz and above.
Click to expand...

To put it clearly- "no". The 7800GTXs have dual-link DVI on one port, possibly the GTs, and the only 6800 Ultras I'm aware of that had dual link were the 512MB models. It's the TMDS issue instead, as others have stated..
 
masteraleph said:
To put it clearly- "no". The 7800GTXs have dual-link DVI on one port, possibly the GTs, and the only 6800 Ultras I'm aware of that had dual link were the 512MB models. It's the TMDS issue instead, as others have stated..
Click to expand...

Correct - there are very few cards that have dual link DVI ports. Before the 7800's, I think there were only the special 6800 Ultras that were produced for Macs to run the apple 30" display (these cards won't work in PC's), and then the higher end workstation class quadras and equivalents.

The current crop of displays running at 1920x1200x60 DO NOT use dual link - they use a single link port, running with a reduced blanking spec (search this forum on that for more details) that squeezes the bandwidth needed into a single channel.

It is only when you get over 1920x1200x60 that you need dual link.

Unfortunatly the terminology causes a lot of confusion - you have dual-DVI (a card with two DVI ports) and dual-link DVI (a DIV port, with all pins wired up, allowing for two channels worth of data over the one connector/cable).
 
the monitor would have to be dual link as well in order to take advantage of that technology.
 
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