Topic Title: Two 4k displays & HD7870
Topic Summary: How to setup two 4k displays
Created On: 01/06/2014 07:54 PM
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 01/06/2014 07:54 PM
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4kx2
Peon

Posts: 3
Joined: 01/06/2014

I bought an HD7870 2GB card and also two (2) 4K monitors each capable of 3840x2160 resolution. I can't get them to both be 3840x2160, one of them refuses and reverts to 1920x1080. I can only get one or the other at 4k, but not both simultaneously. One monitor is connected to the HDMI 1.4a port and one to the Displayport output with an HDMI 1.4a adapter. The box says the card supports UltraHD (4k) resolution and dual monitors is nothing new. If this card is wrong for what I need, what model AMD GPU should I get for powering two 4k monitors displaying at full resolution? Or do I need two cards. This is just display, no gaming. Thanks.

 01/07/2014 03:59 PM
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4kx2
Peon

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Joined: 01/06/2014

Here's some add'l info I neglected to include initially, perhaps it will help someone who may have info about this.

Graphics Card - - Sapphire HD7870 DUAL-X OC 2GB
AMD Catalyst Driver Version 
13.11

AMD Catalyst Control Center Version - 2013.1206.1603.28764

Driver Pkg Version - 13.251-131206a-165817C-ATI

Operating System - 64 bit Windows 7 Pro

Motherboard or System Make & Model - Asrock Z77 Pro4-M
Power Supply - Coolmax CU600B

Display Device(s) and Connection(s) Used
- SEIKI SE39UY04; SEIKI SE50UY04
- HDMI-HDMI CABLE FOR THE 39'; DISPLAY PORT TO HDMI ADAPTER TO HDMI CABLE FOR THE 50"

CPU Details
- INTEL I7-3770

System Memory Type & Amount
- 16GB DDR3 

Additional Hardware
- 240GB SSD 


 01/08/2014 12:01 AM
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Thanny
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Joined: 07/13/2009

DisplayPort Dual Mode (which is what the feature of supporting DVI and HDMI with passive adapters is called) was only updated in early 2013 to support later HDMI revisions.  The card you have is almost certainly limited to sub-1.3 HDMI support, so you can't attach a 4K@30 display via HDMI.

If HDMI is the only connection your displays support, you'll need a second card.  I don't know off hand if the newer R-series cards have a later Dual Mode revision or not, but you might want to look into that, to see if you can simply replace your card instead of adding a second one.

 

 01/08/2014 05:02 AM
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4kx2
Peon

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Joined: 01/06/2014

Of course we are dealing with some unchartered 4k territory here, so there's a learning curve, and that alone makes it exciting. Regarding your comment, well I'm doing what you think is almost certainly not possible!

That is, both Seiki displays are HDMI only for 4k. And on this Sapphire card, thru the native HDMI port connection I can display 3840x2160 @30Hz. Alternatively, on the display port output, with the use of an Accel UltraAV Displayport 1.1 to HDMI Passive Adapter I am also displaying 3840x2160 @30Hz. The card itself offers DP 1.2

The specs for the Accell adapter state "Compliant to HDMI 1.4b, throughput up to 300MHz. Ultra HD 4k x 2k, stereoscopic 3D and Audio. This Type 2 adapter supports 1080p, 3D, and 4k video". I bought that adapter specifically for those characteristics, as many adapters do not state 4k support.

As mentioned when I connect both displays, each port, HDMI or DP, will display 4k on one monitor - but the resultant output on the other port becomes 1080p. I can switch back and forth whether HDMI or DP is in 4k, but each time the other monitor switches to only 1080p.

I can of course just (with $200) get another matching card, but before that, I'd like AMD to tell me officially that one HD7870 card alone can not support 4k on two monitors simultaneously.

Of course we are all just shooting in the dark, which is interesting, but I had thought this forum was where you got official AMD support but apparently AMD either does not monitor posts or ???, as no definitive answer has been forthcoming. I tried calling support but after 45min on hold with a repeating message to wait, I gave up. Frustrating.

 01/08/2014 01:11 PM
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Thanny
Alpha Geek

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Joined: 07/13/2009

This is a user-to-user forum, though there are AMD employees that try to help out when they can.

I'm surprised the passive adapter works as you say.  Either AMD supported faster HDMI through Dual Mode before it was officially released, or I've got the timing of the card's release wrong (no time to check it just now).

I don't know enough about the card's design to do more than speculate on what's really going on, but if I were to do so, I'd say that the equivalent of one Single Link DVI-D and one Dual Link DVI-D is all the available clock sources can handle.  That'd be the same as one HDMI 1.3+ port and one HDMI 1.2- port.

What might work is to get an active DP to HDMI adapter (Accell makes one), which should let you run one 4K monitor as if it were native DP.  It's $33 on their site.

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