Third monitor not working on AMD card

diddums84

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Mar 10, 2013
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Hello folks,

I opened a question about this issue a while back but due to unforeseen circumstances I had to leave the country on very short notice and only got back recently.

The issue is that I've got three monitors connected to my HD6950, one via DVI, one via DVI-VGA, and one via Displayport-VGA.

The first two work fine all the time, no issues there. The third one (Displayport to DVI) works fine whilst the PC is booting and will work for a little while within Windows. It's very intermittent and if the PC goes into power saving mode there's a 20-25% chance that the monitor will "get a signal". I say that because the monitor itself shows that it's getting a signal - IE the power light stays on constantly whereas if they don't get a signal the power light flashes. The monitor however remains black. The backlight is on, the power light stays on permanently indicating a signal, but no picture.

I've tried moving between Displayports and I've tried swapping cables and adaptors around. These are brand new monitors (LG E2242 either side of an ASUS) and I've swapped them around to eliminate a monitor issue. Yesterday I stripped my PC completely and rebuilt if from the ground up double checking all the connections along the way.

This seems to be a very isolated problem as I can't find any info on this. I've updated drivers, Windows (7, 64bit) and made sure everything's up to date.

Some other thoughts, based on internet searching that might be relevant:

Active DVI-VGA adapter. This could potentially be the case but given that the monitor does receive a signal of sorts, I'm inclined to think that the adapter is fine.

GPU power saving mode - Apparently my GPU has a power saving mode that will turn off the displayports until there's a need for them, but again, the signal's there it's just showing a picture.

Another thing to take into account is that if I leave the speakers turned on, I'll hear the "hardware connected" and "hardware unplugged" sound at random intervals. This could happen every 5 seconds, it might not happen at all.

Everything so far is pointing at a faulty graphics card but I need to eliminate this for sure before I go spending a few hundred pounds on a new one, and if this is repairable with a BIOS flash then I'll look in to that too (the card has a dual bios for unlocking the extra shaders and both of them have this issue).

If anyone could shed some light on this I'd be very grateful as it's incredibly frustrating and no matter what I do, nothing seems to solve it.

Apologies for the long post but I wanted to get in as much info as possible. If there's anything else you'd like to know please don't hesitate to ask.

Thanks,
David
 

avjguy2362

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Jun 21, 2012
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I am not clear on your connections 1) DVI to DVI 2) DVI to VGA 3 ) DP to VGA ( via active adapter? ). Correct? I am wondering why you are using VGA connections on the new monitors instead of DVI? Are you running AMD's 13.1 display driver? I have a Sapphire 6950 Flex with 5 monitors connected: 2 DVI to DVI monitors, 2 DP to DVI with Accell Active adapters ( AMD Certified ) and 1 HDMI to HDMI on a 42" TV. In general I have had no problems, exept when I had AMD's 12.9 Driver, one of my active adpators was intermittently changing to a much lower res and I had to restart to get it back, but since changing to the 13.1 driver, I have had no problems. Just wondering why VGA instead of DVI, being that your monitors are new? I would assume that your best connections would be 2 DVI to DVI and 1 DP with an active adapter to DVI. Do any of your monitors have HDMI?
 

diddums84

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Thanks for the quick reply. Unfortunately the two LGs (E2242) only have VGA inputs so that's all I have to work with. The ASUS in the middle has them all, so I can connect anything to it. I am running Catalyst 13.1. Could a non-active adapter display an intermittent picture? If that could be the case then I'll need to make sure I get an active one but I was under the impression that it wouldn't work at all, but it sometimes does.
 
OK you said that the Asus monitor has them all does it have DisplayPort input? Just thinking if the Asus has DisplayPort input you would be better off using that one for the DisplayPort monitor and eliminating the Active adapter altogether. I know the 3 Asus 27" monitors I have support DisplayPort HDMI DVI and VGA input. As for the Adapter it is Active or it would not work at all. That is not to say there could not be a intermittent problem with it.
 

diddums84

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Mar 10, 2013
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That looks very much like the one I have. Do these cards have a sleep mode? It's almost as if the card goes into that state and is unable to recover. I'd like to disable that feature if the card has it and see if that helps.

For reference, it's a Powercolor HD 6950 2gb PCS++
 
Yes if its a passive adapter you could get intermittent signal. It will likely a send SOMETHING but not the proper signal once it figures out what attached and has priority. On boot up you might get it because the clock is going there instead of one of the other monitors.

2 clocks = 2 non displayport monitors. Period. Display port is capable of sending the clock through a passive adapter though, so its probably the card checking the inputs and deciding which output gets them.
 

avjguy2362

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I saw mention of the sleep mode for the VGA adapters, my active DP to DVI don't have a sleep function. I think the reason that the VGA version does have a sleep mode is that VGA monitors were usually associated with CRT's which were high in power consumption. I am pretty sure you will need one active adapter no matter what, even if you had two DP monitors, you would still need one active adapter for either the DVI or HDMI ports for the 3rd monitor. My understanding ( I could be wrong! ) is the exception is that you can piggy back two DP monitors on one DP port and it would only count as one monitor to the card. So in effect you could connect 4 DP monitors on 2 DP ports without any active adapters!
 

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