# Three monitors on an ATI Radeon 7950



## Stonkey (Sep 12, 2014)

Hello. There are several other threads on this issue, but none of them quite seemed to address my issue exactly. I've got a ATI Radeon 7950 card that I'm trying to use with 3 screens. The card has 2 DVI, 1 HDMI, and 2 miniDisplay outputs. Two of my screens are DVI, and the last is HDMI. Obviously I have the HDMI output set to the HDMI input. I have two adapters for mini->DVI, but no matter what configuration I use, I can't get all 3 screens to show.

From previous threads that I've read, it seems that using the HDMI output is a must (cause most people recommend using an active converter for HDMI to DVI), but I'm already using the HDMI output for one screen. Any guidance on the issue would be most appreciated. Thanks in advance!

Edit: Sorry for the mis-type in the title. Looks like I can't change it, though.


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## The Von Matrices (Sep 12, 2014)

Even though there are two DVI ports and one HDMI port on the card, you can only use two of the three at once since the card only outputs two TMDS clock signals.  The rest of the displays must be native Displayport or use an active Displayport to DVI adapter, which generates the necessary DVI clock signal.

You are probably using passive adapters that are usually bundled with the card.  You _*must*_ use one *active *adapter for the third display to work; the other two displays can be connected directly to the card with no adapters.


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## Norton (Sep 12, 2014)

*note- change your title from *9750* to *7950* 

I ran 3 screens using both DVI's and one Displayport to DVI adapter (i.e. 3x DVI monitors)- you should be able to run your 3rd screen on an Displayport to HDMI adapter

Something like this:
http://www.newegg.com/Product/Produ...ayport_to_HDMI_adapter-_-12-996-111-_-Product

iirc- 3 or more screens require the use of at least one Displayport output


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## newtekie1 (Sep 12, 2014)

AFAIK, you should be able to connect the DVI monitors directly to the DVI ports and the HDMI monitor to the HDMI port and it will work.  On the recent AMD cards you can use all the display outputs on the card at once.


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## Aquinus (Sep 12, 2014)

I'll contribute by saying what everyone else is saying. AMD GPUs only have two RAMDAC clock generators. To add a third DVI, HDMI, or VGA display requires an active (m)DP to xyz adapter to gain that third display.



newtekie1 said:


> AFAIK, you should be able to connect the DVI monitors directly to the DVI ports and the HDMI monitor to the HDMI port and it will work.



Not when AMD GPUs have two RAMDACs or when one DVI port is shared with the HDMI port.


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## newtekie1 (Sep 12, 2014)

Aquinus said:


> Not when AMD GPUs have two RAMDACs or when one DVI port is shared with the HDMI port.



From pretty much every 7950 review from W1z: "Display connectivity options include two DVI ports, one full size HDMI port and two mini-DisplayPorts. *You may use all the outputs at the same time.*"

He says the same thing in the 7970 and 280/x reviews.


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## Norton (Sep 12, 2014)

Found this guide:
http://www.amd-news.com/assets/files/amd-cn/Eyefinity_SetupGuide_v1_AMD.pdf

It's for the older cards so I don't know if there are any other options as @newtekie1 mentioned...

This chart is from pg 3 of that guide:


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## The Von Matrices (Sep 12, 2014)

newtekie1 said:


> From pretty much every 7950 review from W1z: "Display connectivity options include two DVI ports, one full size HDMI port and two mini-DisplayPorts. *You may use all the outputs at the same time.*"
> 
> He says the same thing in the 7970 and 280/x reviews.



In the case of the 7970 review, that's because the card he reviewed only had 1 DVI and 1 HDMI port; the later 7970s and 7950s based on custom boards (like the one the OP has and the ones I have) have 2 DVI and 1 HDMI, in which case you can only use two of the three at the same time.

In the case of the 280X, you can use all ports at the same time, but only if all the monitors are identical.  This is because of an updated BIOS on the card that the older 7970/7950s do not have.  If even one of the three monitors is different, then you need the active adapter.


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## newtekie1 (Sep 12, 2014)

The Von Matrices said:


> In the case of the 7970 review, that's because the card he reviewed only had 1 DVI and 1 HDMI port; the later 7970s and 7950s based on custom boards have 2 DVI and 1 HDMI.
> 
> In the case of the 280X, you can use all ports at the same time, if all the monitors are identical, but this is because of an updated BIOS on the card that the older 7970/7970s did not have.



Read the quote from W1z again.


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## The Von Matrices (Sep 12, 2014)

newtekie1 said:


> Read the quote from W1z again.



W1zzard is incorrect, because he copies and pastes his text from previous reviews many times without checking if it makes sense.  That line did make sense when the card only had one DVI and one HDMI, as the reference boards did, but then he copied his original 7950 review for subsequent reviews, changed the number of outputs, and didn't analyze if the change made sense.  This is the same as how he always had it listed in GPU reviews that HDMI 1.4 and Blu-ray 3D were coming "later this year" (referring to late 2010) and kept using the exact same text even after Blu-Ray 3D was released.


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## newtekie1 (Sep 12, 2014)

The Von Matrices said:


> W1zzard is incorrect, because he copies and pastes his text from previous reviews many times without checking if it makes sense.  That line did make sense when the card only had one DVI and one HDMI, as the reference boards did, but then he copied his original 7950 review for subsequent reviews, changed the number of outputs, and then didn't check if it was factual.  This is the same as how he always had it listed that NVidia didn't support multi-channel LPCM on the 400 series since he just copied his template from the 200 series.



If that is the case, I don't think it is, but if it is then the solution to the OP's problem is to use an active DP->DVI adapter for the 3rd monitor.


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## Aquinus (Sep 13, 2014)

I don't think that W1zz is right. If all 3 worked that would indicate a GPU with 3 RAMDAC clock gens. I seriously doubt that's the case.


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## Stonkey (Sep 13, 2014)

Ok. Thanks for all the input, guys. Looks like I will have to get that DisplayPort adapter.
Do you know if the DisplayPort adapter for the HDMI output will mess with the audio at all? Since the miniDisplayports are already DP, does that mean I'd only need an active miniDP to DVI converter if I used one of those?
Additionally, does this mean that I'm locked into a max of three monitors with this card?


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## Mussels (Sep 13, 2014)

thread title fixed.


you can use more monitors, as long as they use DP/active DP adaptors.


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## The Von Matrices (Sep 13, 2014)

Stonkey said:


> Do you know if the DisplayPort adapter for the HDMI output will mess with the audio at all?


I am not sure about whether it allows audio with active DP to HDMI adapters.  Without knowing an explanation, I would recommend getting one active DP to DVI adapter and plugging the HDMI directly into the card.  This is also a good idea because the DVI adapters are generally cheaper.


Stonkey said:


> Since the miniDisplayports are already DP, does that mean I'd only need an active miniDP to DVI converter if I used one of those?  Additionally, does this mean that I'm locked into a max of three monitors with this card?


The card supports 6 displays, but there are some limitations as you've already experienced.

DVI and HDMI needs a clock signal to operate while DP does not.  The Tahiti GPU in the 7950 only has two clock generators, so it can only support two DVI or HDMI displays out of the box.  Each active DP to DVI adapter creates one more clock signal allowing for one additional DVI display.  If you directly connect a display by DP, it doesn't need a clock signal so you aren't limited by this and you don't need any adapters.

It is relatively cheap to have 4 displays by using use one DVI port, one HDMI port, and two active miniDP to DVI adapters.  To get 6 displays you would have to use one or two Displayport MST hubs in addition to adapters.


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## XSI (Sep 13, 2014)

@The Von Matrices thx for that info even though i use 1-2 monitors and nvidia card this info was interesting so maybe ill avoid problems my self or help others in the future


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## Stonkey (Sep 15, 2014)

Well, I definitely appreciate the information, even if it means that I've got to go spend another $30 to finally get everything working. Haha.


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## HossHuge (Sep 15, 2014)

Good luck Stonkey,  I had nothing but problems with Eyefinity.  I had the right adapters and the dp monitor would cut in and out all the time still.  I hope AMD have fixed their issues.


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## newtekie1 (Oct 24, 2014)

Aquinus said:


> I don't think that W1zz is right. If all 3 worked that would indicate a GPU with 3 RAMDAC clock gens. I seriously doubt that's the case.



I know this is an older thread, but I just though I'd post that at least on the nVidia side it is possible to connect 3 monitors without using display port.  I have 3 HDMI monitors connected to one GTX670 right now. 2 through DVI->HDMI adapters, one with the native HDMI port.  So I believe it actually should be possible for the OP to do it with his HD7950 since AMD has always been ahead of nVidia with their display output ability.






And before anyone mentions it, yes it works with SLI disabled.


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## The Von Matrices (Oct 24, 2014)

newtekie1 said:


> I believe it actually should be possible for the OP to do it with his HD7950 since AMD has always been ahead of nVidia with their display output ability.


You're mistaken that AMD has always been superior; they were behind for over two years.  Once the Nvidia 600 series came Nvidia surpassed AMD in display output configuration by allowing three TMDS displays without adapters.  It took AMD until the 290 series to match that capability.  Arguably Nvidia has always been superior since they allow your to add more cards and use the display outputs on multple cards even if they are in SLI.  AMD restricts you to using only the outputs on the primary card when Crossfire is enabled.

Here's the comparison:

AMD:
HD 4000 series and earlier - 2 TMDS outputs per card
HD 5000, 6000, 7000, and <285 series - 2 TMDS outputs per card + Displayport
R9 285 and 290/X - 3 TMDS outputs per card + Displayport

Nvidia:
GTX 200 series and earlier - 2 TMDS outputs per card
GTX 400 and 500 series - 2 TMDS outputs per card (potential to substitute one for Displayport)
GTX 600 series and later - 3 TMDS outputs per card + Displayport


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## Mussels (Oct 24, 2014)

Its definitely a 'feature' of the AMD cards that the third monitor must always be display port.

tested that myself on 5K and 7K cards - there may be exceptions, but thats definitely the reference design.


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## eidairaman1 (Oct 24, 2014)

Dvi will be phased out for dp,,dp does work for analog monitors since they removed dvi-a/i ports only leaving d...


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## Aquinus (Oct 24, 2014)

eidairaman1 said:


> Dvi will be phased out for dp,,dp does work for analog monitors since they removed dvi-a/i ports only leaving d...


Yes, but DP to Dual-Link DVI tends to require USB power. The power off DP usually isn't strong enough to drive the higher frequency DVI signal that dual-link tends to use.


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## eidairaman1 (Oct 24, 2014)

Good to know but dual link was a duct tape solution thats fading out aswell but just like myself gotta have an adapter to make it work correctly


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