Vostro 460 and P2720 1440x2560 monitor

Your ancient GPU does not do dual Link DVI.

You need Display port on a much newer GPU like a GT1030.

https://www.nvidia.com/en-us/geforce/graphics-cards/gt-1030/specifications/

Much appreciate your very prompt reply speedstep, though the 8600GTS does support dual link DVI, DVI-D and DVI-I, it has two dual link DVI ports.

I am going to try a second dual link DVI cable, though if that does not work I accept that a new GPU with display port or HDMI would be a solution.

However I'd really like to understand why my combo does not work, after all people were running 1440x2560 on 8600GTS's back in the day and must have been using dual link DVI. The difference maybe that then it was dual link DVI to dual link DVI rather than dual link DVI to HDMI.

Many thanks!

The Dual Link you are referencing is DVI-D and DVI-A on the same connector.

You can have one VGA and ONE digital Monitor on that connector.

Its not Dual Digital

https://www.amazon.com/StarTech-com-Splitter-Compatible-Monitor-DVI92030202L/dp/B00KILTAT8

Many thanks for the comprehensive info speedstep!

I've actually just ordered a GT1030 GDDR5 (with 1 x HDMI and 1 x DL DVI ports), I'll run the P2720 on HDMI (though I'll perhaps try it with the DL DVI to HDMI cable out of interest).

However I'd still like to know why it wont work with the 8600GTS as the 8600GTS spec states up to 1600 x 2560 on DL DVI. And the P2720 would not work on any screen resolution with the 8600GTS - so I'm thinking it's a matter of it being a DL DVI to HDMI issue and that an older 1440x2560 monitor with a DL DVI port would work with the 8600GTS with a DL DVI to DL DVI cable.

What do you think?

PS: The dual link I'm referring to is a dual link DVI-D to HDMI cable, not an adaptor.

If I recall correctly it's DVI-I that is DVI-A and DVI-D, analogue and digital in one connector. 

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Its not just the bandwidth thats the issue.

You only have 256 or 512 meg of Video Ram

The GT1030 comes with 2 GIGS video ram.

older GPUs weren't designed to transfer pixels at pixel rates that were higher than 330 MHz, so that automatically became the limit.

2560 x 1440  this is a video mode over DL-DVI. When using CVT2-RB timings, requires a clock speed of 483 MHz, far higher than 330 MHz limit.

1080p @ 60Hz with a pixel clock of 148.5 MHz is fine

HDMI (standard type A) is backward compatible with single-link Digital Visual Interface digital video (DVI-D or DVI-I, but not DVI-A or dual-link DVI). No signal conversion is required when an adapter or asymmetric cable is used, so there is no loss of video quality.

From a user's perspective, an HDMI display can be driven by a single-link DVI-D source, since HDMI and DVI-D define an overlapping minimum set of allowed resolutions and frame-buffer formats to ensure a basic level of interoperability.

HDMI types (type B, while compatible with dual link dvi, does not exist)

The version in widespread use today is the 19-pin Type A HDMI connection, which incorporates single-link DVI-D.

A Type B version of HDMI has been defined with 29 pins, which incorporates dual-link DVI-D.  It does not exist in practice.

PS 

Many thanks redxps630, another very comprehensive reply!

My understanding is that DVI-D is compatible with standard HDMI though single link DVI will only handle up to 1200x1920 where as dual link DVI will handle higher resolutions, as does standard HDMI. Hence the 8600GTS is quoted as being dual link DVI as it can handle 1600x2560.

Having researched this a little further it seems that you can drive a 1440x2560 monitor that has a DVI port (dual link due to the resolution) by using either a dual link DVI cable or by using an HDMI to dual link DVI cable (though not an HDMI to single link DVI cable).

Though this does not work in reverse, i.e. you cannot drive a 1440x2560 monitor that has an HDMI port (and no DVI port) by using a dual link DVI to HDMI cable.

So my 8600GTS (dual link DVI only) will only drive an older 1440x2560 monitor that has a dual link DVI port via a dual link DVI cable. Though it won't drive the P2720 as this doesn't have a DVI port.

This is not a definitive answer by any means though seems to align with my experiences.

Thanks again!

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I am running the P2720 now with a Palit GT1030 card via HDMI and all works fine, though I don't feel that I am getting the rock solid colour/gamma stability that I had with the 8600GTS on the P2421 and previous Dell monitors.

Any thoughts would be welcome?

Thanks!

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