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Comment by jrockway | Hacker News Reader

Depends on what OS you use. If you use Linux, yeah, you're screwed. They are still arguing over how to support monitors that expose themselves to the OS as two monitors. The current answer is "that's dumb, maybe they'll go away." It is dumb, but they're not going away.

Over on Windows, Nvidia has some hacks in the driver to work around this. With a $70 current-gen card, I can drive two 4k monitors at 60Hz. One monitor connects via two HDMI cables; the other over Displayport MST. (I don't actually have two 4k monitors, but I did convince my computer that my one monitor was two to test this.)

You're right about getting 4 monitors working. Probably possible with an SLI setup, but the current generation of video hardware makes 1-3 monitors easy and 4+ monitors hard. 3 monitors is better than a few years ago, though.

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Nvidia limits multiple monitors on their consumer cards to 2 monitors and 1 gpu or 2 gpus and 3 monitors in an surround (SLI) setup.

For their professional series of gpus they offer premium mosaic which allows up to 4 monitors on a single card[1].

AMD allows up to 6 monitors on a single consumer card with Eyefinity[2].

Of course through the use of splitters and multiple cards it's possible to attach more monitors. I've personally setup a 12 display system off a single card. There are of course performance limitations when you only have one gpu and a large grouped display.

For what it's worth I've had an easier time setting up multiple monitors in Linux then I have on Windows.

1: http://www.nvidia.com/object/quadro-k5000.html

2: http://www.amd.com/en-gb/products/graphics/desktop/5000/5870...

Wait, how is a monitor that appears as two to the OS a problem? We've had multi monitor support for a long time, this is just the panels/pixels stitched closer together, isn't it?

The problem is you'll have two copies of your desktop (or whatever you choose to have 1-per-monitor of) on one physical screen, because the OS thinks it's two monitors when it's actually one monitor.

To make this go away, all that clever support needs to be disabled, which is actually currently impossible in Linux!

I thought Linux supported extended desktop, but come to think of it, I never actually tried it. Windows always worked perfectly fine :-)

Are you saying that there is some kind of dropoff, where current GFX hardware has the horsepower to drive 3 large screens easily but not 4?

I'm saying current-gen hardware puts three ports on the card by default. ATI does it, NVidia does it, and Intel does it.

Ah, I see. My GFX card has something like 5-6 ports (4 mini-DP ports and 1-2 DVI) so I've never had that problem

Are you doing your development on a remote computer via putty then?

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