Best guesses, in order of most to least likely:

* The output resolution of the video more running on the 660 may be set too high for the Dell monitor to handle.

* The output frequency of the video mode running on the 660 is set too high or too low for the Dell monitor to handle.

* The drivers installed for handling whatever monitor you were using prior (yes, even the monitors need drivers to determine frequency limits and such) might be incompatible with the Dell monitor.

* The monitor may simply not like having the signal converted in that fashion.

My money is on option 3 or 4 since this is a 4k monitor that I picked up on a close-out deal. There shouldn't be any resolution under 4k that it shouldn't be able to handle (I wouldn't think, anyway).

4K Monitor... My bet is on the cable.

Solarstorm wrote:

4K Monitor... My bet is on the cable.

But how could the exact same cable work with a laptop but not with the desktop? Or work briefly and then not at all? That makes no sense.

Having another working monitor while you're setting up the new one would help. Have you tried running your Dell at native res (4K/UHD) but at 30Hz? This could tell you something about bandwidth or configuration issues (e.g. problems with the monitor trying to run 60Hz via single stream or multi stream)

What Dell model exactly? More info on card model and driver version might also help (if you're asking this on Dell's support forum that is).

OK, I just tested a HDMI cable that's supposedly "High Speed" but it failed to display 3840x2160 @30Hz or 1920x1080 @60Hz. It's just not detected at all. Win8.1 on a Haswell laptop.

Whereas the supplied cable (a bit short, only 1.5m or less) from LG works at the above settings (I don't have HDMI 2.0-capable device to test full res @60Hz).

I wondered if it was a length issue, but that cable is only 3m, so not that long. I'll have to buy a new cable. 😒

Well mystery solved, looks like neither the display port nor HDMI cables were
able to seat properly due to the way the adapter back plate was positioned.
Would have been nice if the socket locations were more centrally positioned.
I thought I had the adapter positioned square in the slot but perhaps the
screw torque caused it to skew slightly. I never used to have this problem
with single slot cards, seems to happen only on dual slot cards (which is most
amid to high end cards these days).

Great!

Does the GTX 660 work at 60Hz (3840x2160 res)?

I made another thread recently while looking for cheapest/minimum required cards to drive UHD/4K at 60Hz. EIZO listed GTX 660 as minimum iirc, but my LG manual says 960 for NV GTX series. So I'm just curious.

GTX 660 should work at 60Hz, on the displayport connection. http://www.geforce.com/hardware/desktop-gpus/ … /specifications

Sorry, my question wasn't complete.

Does the GTX660 support UHD/4K @ 60Hz over SST (single stream transport aka not tiled)? Or only via MST?

archsan wrote:

Sorry, my question wasn't complete.

Does the GTX660 support UHD/4K @ 60Hz over SST (single stream transport aka not tiled)? Or only via MST?

I'm honestly not sure how I'd tell the difference. There is no visible
flickering or artifacting at 4K compared to the other resolutions.
Or would it say in the display properties it's working at 60hz?

Yes -- or in "Nvidia Control Panel" if you have it shown when you right-click on the desktop (in my intel laptop it's "Graphics Properties"). At least that will show you the refresh rate.

As for information on whether you're on SST / MST... I'll have to look it up. (I still don't have a DP-enabled card at the moment!)

This is what I have found about SST requirement, but I don't see it mentioned in graphics card specs:

The main requirement for supporting 4K@60 on DP SST (single-stream transport) is that the core display clock (CDCLK), which is configured by SBIOS, must be set high enough to drive the dot clock required by the mode. Usually 4K@60 has a 536MHz dot clock, so it requires a 540MHz CDCLK. If the system OEM did not configure the CDCLK at 540MHz for thermal, power saving, or other reasons, then the system will not be able to drive 4K@60 over a single DP stream.

source: https://communities.intel.com/thread/51410

Apart from supposed advantages of SST over MST (more straightforward, less hassle / potential problems), I'm also thinking what if there are monitors that support only 4K/UHD @60Hz via SST.

Anyway, thanks for bothering--didn't mean to hijack your thread. 😀