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TechaGek · ‎11-19-2015

As the title says, is it possible to run 2 PG278Q's at 144Hz while running the 1 PG279Q at 165Hz, but using it as the main monitor?
Or would I need all three monitors running at the same refresh rate?
I feel like a complete noob with this post.

Korth · ‎11-19-2015

The PG278Q and PG279Q both have 2560x1440x24bpp native resolution, and they are both DisplayPort 1.2.

NVidia multi-display technologies (3D Vision, 3D Surround, HD 3D, nView, Mosiac) support up to three displays - provided they each have identical resolution, identical colour depth, identical refresh rates. Reference NVidia GPUs do not support mixed pixel densities, mixed frame rates (outside of G-Sync), daisy-chaining, or multiple discrete display outputs - nonreference NVidia GPUs might provide more DisplayPort outputs but never dare to redesign the fundamental GPU architecture.

Recent NVidia GPU cards are all DisplayPort 1.2 (at best). Reference NVidia GTX780 cards and your EVGA GTX780 SC card have a single DisplayPort 1.2 output.

DisplayPort 1.2 supports a signal bandwidth up to ~17.28Gb/s HBR2 (after removing overhead costs). DisplayPort 1.3 supports more signal bandwidth (up to ~25.92Gb/s HBR3) but requires fully-DP1.3 hardware architecture in the GPU's ROPs and display panel's embedded logic board - it's far more involved than simply installing updated firmwares or a better DP cable.

2560x1440x24bpp@60Hz requires ~5.31Gb/s (which increases to 5.80Gb/s CVT-R or 5.63Gb/s CVT-R2 after screen timing/blanking overheads).
2560x1440x24bpp@120Hz requires ~10.62Gb/s.
2560x1440x24bpp@144Hz requires ~12.74Gb/s.
2560x1440x24bpp@165Hz requires ~14.60Gb/s.

There is only enough DP1.2 signal bandwidth to support up to three 2560x1440x24bpp monitors at 60Hz - or a single 2560x1440x24bpp monitor at 120Hz, 144Hz, or 165Hz.

Your 2560x1440x24bpp monitors cannot operate together as 2x144Hz and 1x165Hz - they will each operate at 60Hz if two or three are used together with a NVidia GPU card(s). (The software and firmware might allow you to tweak two 2560x1440x24bpp monitors to operate at 85Hz each - but this is very nonstandard.)

Your monitor hardware and GPU hardware simply cannot support any other configuration.

"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]

TechaGek · ‎11-20-2015

Awesome, thank you for the detailed reply. It's much appreciated!
Even if I were to run a 3-way SLI setup, using a DisplayPort on each card. Would that not allow me to run all three screens at 2560x1440x24bpp 165Hz? I'm planning on upgrading to Broadwell-E & nVidia Pascal in the near future, so this is a formal strategy. Meaning I want to get this right before I upgrade any further.

Korth · ‎11-20-2015

Even if you pair three SLI-bridged GPUs directly to three Swift monitors with three DP cables you cannot normally obtain >60Hz refresh rates on a single multi-screen display. You might be able to run each monitor at >60Hz if they're used as isolated individual displays, but who wants to run three desktops or three productivity apps at >120Hz?

This is an NVidia hardware limitation. SLI-bridged cards are treated almost like one big fat clumsy GPU, the SMX and CUDA capacities are combined towards single task - calculating and rendering the frames of a single-screen or multi-screen image - and they use many very clever technologies (like warp and shuffle instructions, Hyper-Q pipelines, Grid Management Units and CUDA Work Distributors, Dynamic Parallelism, and distributed GPUDirect tiers) to maximize sustained utilization of GPU hardware resources. But the final DP outputs of all GPUs in the SLI-bridge are still limited by the DP limitations hardwired into the "primary" GPU.

So - yes, the DP cables should be able to carry enough display data to run your monitors at full spec. But - no, your NVidia GPU architecture will not support it.

120Hz+ gaming monitors are sort of a new thing, Kepler and Maxwell (and Tesla) just weren't designed to run a multi-display at extreme refresh rates. Pascal is anticipated to use DisplayPort 1.3 (which has technically been around since before Sep/2014) and I expect Pascal GPUs will be designed to run multiple 120Hz monitors in the sort of multi-display setup you describe.

You're obviously planning to upgrade your single EVGA GTX780 SC to a multi-GPU SLI setup. I would recommend waiting until Pascal GPUs are introduced, if they can drive your killer monitors at full refresh then buy Pascal, if they can't at least maintain a triple-monitor display at 120Hz per display then instead buy into GTX980Ti or Titan X cards because they'll get knocked a rung or two down the exponential price ladder (plus you'll see the final evolution of these GPU cards, fastest factory-overclocked silicon, most refined VRM circuits, best components and cooling).
Maybe pick up another GTX780 (or two) cheap off craigslist to hold off the upgrade urge until Pascal actually launches, lol, probably sometime around Q2/2016.

"All opinions are not equal. Some are a very great deal more robust, sophisticated and well supported in logic and argument than others." - Douglas Adams

[/Korth]

2x PG278Q @ 144Hz, 1x PG279Q @ 165Hz.