Topic Title: Can't Run CrossFireX With New Monitor Through DisplayPort 1.2 Connection
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Created On: 05/10/2014 04:07 PM
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 05/10/2014 04:07 PM
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Escovado
Peon

Posts: 15
Joined: 05/10/2014

My system has worked perfectly for a year now with my old Dell 24” 1920 x 1200 resolution, flat-screen monitor with a DVI connection.  I just bought a new LG 34UM95 wide-screen monitor.  If I use the HDMI input on the new monitor (Mini-DisplayPort to HDMI cable), everything works flawlessly—but I’m stuck with a 30Hz screen refresh rate that is no good for games.  However, if I use the DisplayPort 1.2 input (Mini-DisplayPort to DisplayPort cable), I can get a 60Hz refresh rate, but the system crashes (auto-reboot, no blue screen) the moment any application switches into full-screen graphics mode.

I am running two Radeon 7990s in CrossFireX (4 GPUs).  If I disable CrossFireX, then I can use full-screen graphics through the DisplayPort input at 60Hz.  If I enable CrossFireX, then the system crashes when switched into full-screen graphics.  It makes no difference what the screen refresh rate is set to (30, 50 or 60Hz), or the resolution (native 3440 x 1440 or scaled down), or which driver is installed (Catalyst 14.4 or 13.12), or if anything is overclocked or not: If CrossFireX is enabled to the DisplayPort input, the system immediately crashes (reboots) the moment full-screen graphics is turned on.

The system event logs don’t give any useful information.  A “Critical” “Kernel-Power” error message is logged that says, “The system has rebooted without cleanly shutting down first. This error could be caused if the system stopped responding, crashed, or lost power unexpectedly.”

I also tried different cables and different outputs on the 7990s.  Same result.

Anyone have an idea what I can do?  I’d really like this monitor, but I’m not going to remove my second 7990 graphics card.

Graphics Card
Two Radeon HD 7990s in CrossFireX.

AMD Catalyst Driver Version, and Driver History
Catalyst 14.4 and 13.12

Operating System
Windows 8.1 x64

Motherboard or System Make & Model
Asus Rampage IV Extreme

Power Supply
Lepa G1600W

Display Device(s) and Connection(s) Used
Monitor: LG 34UM95 (3440 x 1440 native resolution);  Connection: DisplayPort 1.2 (Mini-DisplayPort to DisplayPort cable) and HDMI  (Mini-DisplayPort to HDMI cable).

Applications and Games

All applications running in full-screen graphics mode fail.

CPU Details
CPU: Intel 4930K @ 4.4GHz (overclock on CPU makes no difference)

 

Motherboard BIOS Version
American Megatrends version 4403

System Memory Type & Amount
32GB Corsair, DDR3  @ 1866MHz

Additional Hardware
SSD, HDD, Blu-Ray Drive, lot of fans in water cooled system



Edited: 05/10/2014 at 09:03 PM by Escovado
 05/12/2014 11:57 PM
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Peon

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Joined: 05/10/2014

No one knows?  Anyone from AMD read these forums?  I'd like to know officially at least that I'm SOL. 

 05/16/2014 02:45 PM
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Peon

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I have an update:  I did some more experimenting and re-installing drivers, etc.  I even went through the hassle of switching the cards.  I have established that the LG 34UM95 does work with CrossFire enabled at all the supported resolutions below the native resolution of 3440 x 1440.

 

I also got a hold of a Samsung UD590 4k monitor and plugged it into the same connector.  The native 4k resolution of 3840 x 2160 works perfectly with CrossFire enabled.

 

It's been narrowed down to this: It's the 3440 x 1440 resolution only with CrossFire enabled that's crashing the video cards. I did finally get a hold of AMD.  I passed the updated information on to AMD and added it to the support ticket.  Hopefully they will have a fix for it in a driver update.

 05/29/2014 11:33 AM
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Peon

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Joined: 05/10/2014

Catalyst 14.6 beta drivers did nothing to fix this problem.  Still waiting to hear anything back from AMD.  Bumping the thread.

 06/13/2014 07:08 PM
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Thanny
Alpha Geek

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It didn't click for me the first time I read this thread, but I think you're SOL.

I never thought much about the Crossfire bridge until some older threads about problems with 144Hz displays brought to the fore a limitation - the bridge only transfers at about 900MB/sec.  If you have a 1920x1080@144 display, a single bridge isn't fast enough to carry the frames from one card to the other.  The solution, which amazingly works, is to use two bridge connectors, to double the available throughput.

You're adding pixels instead of refresh rate, but end up with about the same bridge throughput requirements.  Since you only have one bridge to work with, however, doubling up isn't an option.

Ultimately, you just have an incompatible combination of hardware.

Your options seem to be these:

1)  Ditch the monitor.  Go with less wide models (2560x1600, 2560x1440), or a set of three screens to duplicate something like the same effect.  One bridge correctly handles 2560x1600@60, and Eyefinity setups seem to have a workaround in place (though I don't know what).

2)  Ditch the 7990's and go with 290 series cards, which abandon the CF bridge and instead use the PCIe bus.

3)  Hope that the workaround used for Eyefinity can be adapted to a single over-large screen, and wait for AMD to implement it.

If you go with option #2, the fake currency fad might help you get a good price for the 7990's.

 

 06/13/2014 08:22 PM
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Peon

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Joined: 05/10/2014

Thanny,

Thank you for your reply.  My later posts in this thread clarify what is happening.  You assume that my system has a bandwidth problem [Edit: if I'm reading you correctly], but that is not the case:

I tested my 7990 crossfire set up with a 4k monitor runnig at native resolution (3820 x 2160 pixels) and my system worked perfectly with crossfire enabled.  Since a 3820 x 2160 resolution is pushing 68% more pixels per frame than at 3440 x 1440, the problem is not bandwidth related. All other resolutions (higher and lower) work perfectlly with crossfire enabled.  It is the 3440 x 1440 resolution only that crashes when switching to full-screen graphics mode with crossfire enabled.

Since the native resolution of my monitor is an oddball size (3440 x 1440), and given that this monitor is both brand new and hard-to-find at this point, it is safe to conclude that AMD has not had a chance to do any testing with this monitor.  It appears that AMD's drivers have a bug in them when dividing up a frame of this particular size under quad crossfire.

If the crash is indeed caused by a bug in AMD's drivers, then replaceing my two 7990s with a pair of 295x2s probably won't make any difference since the same driver software will be running those as well.



Edited: 06/14/2014 at 12:10 PM by Escovado
 06/15/2014 08:09 PM
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Thanny
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Are you sure it was a single 3840x2160 screen at 60Hz?  Many (most?) 4K displays present a single logical screen for 3840x2160@30, but two logical screens (to be merged together in with Eyefinity) for 3840x2160@60. 

If that's what you tried, then you didn't rule out CF bridge bandwidth as the source of your problem.

If you can manage to trick the drivers into doing 3440x1440 at 30Hz, you could rule out the resolution specifically as the problem, and make a strong case for CF bridge bandwith.

 

 06/15/2014 09:22 PM
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Peon

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The 4K monitor I tested was the Samsung UD590 Series U28D590D.  I connected it to the same DP output as my LG 34UM95.  Windows reported the Samsung monitor to be running at 3820 x 2160 @ 60Hz.  It looked like 60Hz and it certainly was a 4k resolution.  I tried it with crossfire on and off.  It worked without a hitch.  It has only one DP input like my new LG monitor and Windows reports it as being a single display.

It doesn't make any difference what the refresh rate is set to with my 3440 x 1440 monitor.  Crossfire enabled at the native resolution causes an instant reboot when full-screen graphics is enabled.  I don't know what else I can say.

You mentioned using eyefinity to merge two logical displays together.  I see one display for this monitor.  IS there anyplace I can check to see if there are two logical displays available in this monitor?

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