Sharp LC-43UB30U 43" 4K tv and Radeon 6950 Crossfire

[silent-circuit]

I realize I'm way outside the bounds of what this combination is "supposed" to do, but that's what people seem to do here -- push it -- so I'm hoping I'm in the right place.

I've got the TV hooked up via a passive HDMI to DVI adapter (one of the little screw-on things) to a known high quality DVI dual link cable connected to the first DVI port on my primary 6950. The other card is in Crossfire using 2 bridges -- I read that this is required for higher pixel clocks in some cases.

First question is, is there any reason I'd be better off using a straight HDMI cable, from the card's HDMI port to the TV? I figured since the card is HDMI 1.4 and everything I read says you need 2.0 to get 3840x2160 I would be better using the DVI port and the adapter, but maybe I'm wrong there?

Initially the display only showed 1080P as an option, but after patching pixel clock with the AMD utility available here and then using CRU to set a custom resolution, it is /supposedly/ running at 3840x2160 @ 60 Hz.

The problem is it really, really doesn't feel like 60Hz, it feels crazy slow, maybe even under 30Hz. There was always some mouse lag with this display but now there's not just a delay -- I literally see the cursor "strobe" across the screen when moving it.

That said I've literally never used a display this high res or this big before, so I don't know what to expect. Is this normal behavior for Windows? Am I not running the res I think I am? Is there any way to check other than the Windows Screen Resolution page? If I go in to the Advanced options under Monitor there it says 60 and will let me set 59, etc, but 30Hz and 60Hz feel basically the same. I can certainly tell the difference between 30 and 60 FPS, so this is throwing me off big time.

It's probably worth noting that I haven't tried to game on this display since the resolution switch, so I'll come back shortly with impressions there and see if 30/60 makes a difference. The whole "strobing mouse cursor" thing just has me confused.

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Alright, after a little more messing around I realized the display gives info on audio and video format right after you change inputs.

Based on this, it's running 2160P (full res at least, yay?) at 30Hz despite Windows reporting 60Hz set. It's probably worth noting I turned Crossfire off just to be safe.

Is there any way around this limitation? I was under the (apparently mistaken) impression that the pixel clock patch would fix it.

Will I have to get a new GPU if I go to a 4K display, or do you think it's an issue with this model of TV specifically?

My understanding with continued research is it won't run 4:4:4 chroma 4k @ 60Hz from a PC anyway -- or at least no one has managed it yet -- I'd love to be the first! -- so I will probably be exchanging it for the much more expensive Samsung 40" 4K.

Before I do that though I'd love to know if my cards can even push the res in Windows at 60Hz -- or do I really need a new Nvidia 9 series as bad as people say?

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A little more info.

2160p@30Hz via the DVI port via DVI cable and passive HDMI adapter
2160p@30Hz via the HDMI port with a straight HDMI cable (not an officially 2.0 qualified cable, but it's like 6 ft and good quality)

HDMI port used on the TV also doesn't seem to matter, though I've read many places that on these lower end sets (and on most sets really at this point) there's only one that's really HDMI 2.0. Sadly, despite reading a few places that that's the case with this set, I haven't seen anyone clearly state which port is supposed to work...

This is with pixel clock patched and CRU set custom res.

So far nothing lets me get 60Hz.

Would love some help with that.

Frustration is setting in -- am I better off with one of the Korean 40" displays like the Wasabi Mango with native DisplayPort? It would be a little less than the Samsung TV I'm looking at, with the downside of around a 2 week wait for shipping.