Support of 3840x2160@60Hz without MST mode is limited to a select few Haswell models though (Haswell-H). The data sheets for the others say 3840x2160@30Hz, but are technically capable of driving 3840x2160@60Hz in tiled mode (using DisplayPort 1.2's MST feature). Reviews of current 4K screens say there's no GFX card actually driving a 4K display at 60Hz without MST. MST does require appropriate driver support and I've yet to find an official statement stating that intel officially supports that (a few months back there was a stucky up that said such support was under consideration), yet Asus has a video up that tells you you can use intel's collage mode to driver their tiled mode 4K display (tiled mode meaning the display acts like two 1920x2160 screens... so it's two displays, thus requiring Displayport MST and hence requiring driver support to make the whole thing appear as one screen).
Interestingly, it seems the Samsung screen is single tile. However, that means you could be running into the limitation of most Haswell chips. Except for the H series, they are not rated for doing 3840x2160@60, only at 30Hz (at least that's according to the data sheets). So for instance the U models used in Ultrabooks, can only work in tiled mode.
I only have a tiled 4K screen - so somebody with a non tiled model would have to say whether the latest drivers change anything. As far as I gather from the datasheet, the non -H Haswell models won't handle those displays. But they support the tiled screens just fine, if the necessary drivers are installed.
Or can you get a non tiled 4K display working on an Haswell U processor? If the silicone doesn't support HBR2, I doubt that will ever work before replacing the CPU with a Broadwell model.
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. Also, Haswell ULT (-U) and ULX (-Y) are limited to 450MHz and 337MHz CDCLK, so they will not be able to do 4K@60 SST. ULT should still be able to do 4K@60 MST, though. ULX can’t because 4K MST still requires HBR2.
This shouldn’t affect DP MST tiled displays because for those we use two streams, each for one half of the display, reducing the pixel clock.
Additionally, 4K support is only available on the Core processor graphics. Celeron and Pentium do not support 4K. All Core Haswell processors will support HBR2 with the exception of Haswell ULX.
Here is a reference guide that can be of help.
Excerpt from above:
Processor 4th generation Intel® Core™ processor family (Intel® Iris™ Pro Graphics 5200 / Intel® Iris™ Graphics 5100, Intel® HD Graphics 5000 / 4600 / 4400 / 4200) 3rd generation Intel® Core™ processor family (Intel® HD Graphics 4000 / 2500)
Maximum Display Resolution
Higher pixel resolutions allow the PC to show more image detail.
DisplayPort* 1.2 / eDP*
H-Processors: 3840 x 2160@60Hz
U-Processors: 3200 x 2000
@60 Hz, 3840x2160@30Hz
Y-Processors: 2560 x 1600
@ 60 Hz
HDMI* 4096 x 2304, 3840x2160 @ 24Hz / 24bpp
DVI 1920 x 1200 @ 60Hz
Your findings are really spot on. They are very useful.
I took my i5-4690K processor on a H97 motherboard to Best Buy to plug a DP 1.2 cable, from the PC, to a Panasonic AX800U 4K TV. I adjusted the DP settings on the AX800U to SST.
I achieved on WQHD 2560x1440@60HZ. I was so close to 3840x2160@60Hz.
What kind of 5th generation processor for a desktop, will allow me to achieve 3840x2160@60Hz?
It has been (5) months, we are waiting for your answer to which Intel processors for desktop has a 540Mhz CDCLK rate for the valid processor support of 4K (3840x2160@60Hz) mode using DP/1.2 set to SST or a configuration that will achieve the 4K (3840x2160@60Hz) on a UHD television. As I state above to robert_u, I can acheive WQHD 2560x1440@60Hz as the best resolution.
I feel Intel should be able to provide a rapid and simple explanation/instruction to create results in the real world of 4K (3840x2160@60Hz) on DP 1.2. We need enjoy the 4K resolution at 60Hz that we were promised and paid for.
We are choosing this route DP 1.2 (3840x2160@60Hz) because HDMI 2.0 at 3804x2160 only provides 30Hz bandwidth capacity at the best. 30Hz at 4K is just plain useless for action subject matter like a sports event or movie.
We await a response, please.