AMD Radeon HD 7870 not feeding a third display

[James Lawson]

So after many struggles with my pc, I've finally got my AMD Radeon HD 7870 working.. sort of.

Currently I run three monitors, a Samsung SyncMaster P2250 (DVI) and two Dell E177FP (VGA) - however I'm having issues getting the third monitor to display an output.

The way I lead to believe I could get this to work, was to have my Samsung screen going straight into the digital only input on the card, one Dell screen to be converted from VGA to DVI and input that into the DVI/Analog input, and then finally on my last Dell screen have another converter from VGA to DVI plugged into a DVI to mini displayport adapter which would input into the one of the two mini displayport inputs on the card.

The third input (which ever gets plugged in last) does get picked up by windows, however it doesn't show an output on the screen. Here's where it gets even more weird, if I only plug in my Samsung screen/DVI cable and one Dell monitor via VGA>DVI then DVI>Mini displayport I get an output on both two screens, however in windows screen resolution it displays three inputs still.

If I only wanted two screens to work (DVI & either mini dp or VGA>DVI) then it would be fine, however I was lead to believe that I could run up to four screens from this card.

I also have some images of all my cables below. Also my DVI>Mini Displayport adapter is the "XFX Mini DisplayPort to Active Single Link DVI Dongle".

http://www.cclonline.com/product/54857/MA-AP01-ND1K/Video-Cables/XFX-Mini-DisplayPort-to-Active-Single-Link-DVI-Dongle/CAB1265/

I'm hoping that it may just be a setting to switch around, or an adapter (even though they all work singly.

Thank you, much appreciated!

 

[freedom7]

Are all 3 of your monitors VGA only ?

 

[James Lawson]

All but one, so basically both (2) Dell's, and then the Samsung is DVI

 

[freedom7]

Then have you tried with the DVI on into the display port adapter and the 2 vga'a into DVI ?

 

[Novuake]

You are trying to adapt a digital only output to a analog output. Its not gonna happen unless you buy a quite expensive converter to do this ACTIVELY, these units usually require power separately just to give you an idea. For a little more you can buy a DVI monitor.

Buy a DVI monitor AND an ACTIVE DisplayPort to DVI adapter. Both those are required for more than two displays. you have neither.

 

[freedom7]

This image shows ou how you can connect to AMD cards if your card is Flex ( don't know if your card has Flex ) compatible then you should be able to connect them but if its not the you need monitors with HDMI, DVI or Display Port out puts.

http://www.sapphiretech.com/Flex/FleX_Eng_apply.html

As long as the "XFX Mini DisplayPort to Active Single Link DVI Dongle". you have quoted above is an active converter then you will be able to use this.

 

[Supermuncher85]

Did you select the monitor and click on the extend display under the windows display properties? Since they are showing up.

 

[James Lawson]

Then have you tried with the DVI on into the display port adapter and the 2 vga'a into DVI ?

The top DVI is for VGA>DVI converters and the bottom one is a digital only input, ie you can only plug DVI cable in (no converters)

You are trying to adapt a digital only output to a analog output. Its not gonna happen unless you buy a quite expensive converter to do this ACTIVELY, these units usually require power separately just to give you an idea. For a little more you can buy a DVI monitor.

Buy a DVI monitor AND an ACTIVE DisplayPort to DVI adapter. Both those are required for more than two displays. you have neither.

This is exactly what I thought.. however if I unplug the other analog monitor (VGA>DVI converter) then the VGA>DVI>Mini DP system works flawlessly with the Samsung monitor connected (DVI cable).

Did you select the monitor and click on the extend display under the windows display properties? Since they are showing up.

Yeah already tried.


Question to all:

Surely it wouldn't be showing up in 'CCC' or 'Windows Screen resolution' if the active mini displayport adapter wasn't going to be able to convert the analog input?

I'm most likely wrong, I just can't understand why.

 

[Supermuncher85]

Well I'm guessing the whole display port to dvi to analog is what's messing this up. What brand is that GPU?

 

[Supermuncher85]

So my guess is, that it's creating a digital only signal from the DP -> DVI.

Can you actually get any output on the VGA monitor using that cable combination without having the other monitors plugged in? If the answer is no, I would suggest getting a DP -> VGA adapter.

 

[James Lawson]

It just says AMD, weirdly though it won't show an output anymore by itself (I'm sure it used to).

So a VGA > Mini Displayport will complete the fix? Something like this http://www.pcworld.co.uk/gbuk/pc-accessories/cables-and-power-accessories/mains-monitor-cables/iwantit-imdpvga12-mini-displayport-to-vga-adaptor-0-15-m-13828409-pdt.html

If so I might be able to grab one tonight as they close at 8pm and it's only just gone 6:10

 

[James Lawson]

To finish off this thread, I went out sceptical and bought a VGA > Mini displayport adapter.. I was told it wasn't active as it didn't have any power going into it but it works like a charm!

http://www.maplin.co.uk/mini-displayport-to-vga-adaptor-454320 It doesn't look like that image, it's more like a remake of Apple's version. It also supports heights outside of 1200 by the looks of things.. I have my two Dell Monitors portrait for my audio production and its fitting perfectly.

Much appreciation for the help guys!

 

[Supermuncher85]

Good thing. As far as I can tell, you can extend using passive adapters, but cannot run eyefinity.

Lastly not all active adapters require a 'powersupply' (extra usb cable). Just like the XFX adapter you had was active, without extra cables.

Glad it works!