4 Monitor Setup Issue with HD7870

MEB2003 · Oct 7, 2013

I am using a Gigabyte HD7870 and am currently running a 3 monitor setup.

- 1x DVI
- 1x HDMI
- 1x Mini Display Port

I recently wanted to add a 4th "monitor" (my TV) to the setup. I am using an HDMI to Mini Displayport cable, and the computer will not permanently recognize the 4th display.

The computer registers the 4th monitor but only momentarily. It gives the sound that a device has been connected and then the display dissapears on the display settings screen. The process then repeats itself over and over.

Would the issue be with the cabling or can the card not handle 4 displays at once?

Thanks for your guys help!

Supernova1138 · Oct 7, 2013

The 7870 should be able to do four displays, so that isn't an issue. Have you tried hooking up your HDMI monitor to the mini Display Port adapter and the TV to your HDMI port to see if the card will pick it up that way?

MEB2003 · Oct 9, 2013

Supernova1138 :

I just tried this. Picks up the TV now but does not recognize the monitor.

Supernova1138 · Oct 9, 2013

Looks like there is an issue either with that specific Mini DisplayPort, or a problem with the HDMI to MiniDisplayPort adapter, verify that both mini Displayports function with your MiniDP monitor, if they do, you may have to get a different adapter.

jaguarskx · Oct 9, 2013

The issue is that "Eyefinity" can only recognize up to three monitors. It seems your HD 7870 has 4 ports:

DVI x1
HDMI x2
DisplayPort x1

That is not unusual since that give you the following options for EyeFinity:
1. DVI, HDMI, DisplayPort
2. HDMI, HDMI, DisplayPort

The issue is that most graphic card only has one chip called RAMAC which output video signals to monitors. Each RAMDAC can only send two video signals. Therefore, no matter how many ports a graphics card has, only two of them can be used at any one time.

Cards with DisplayPort has a RAMDAC chip devoted solely to the DisplayPort (to the best of my knowledge). The reason for this is because DisplayPort supports up to 2560x1600 resolution. For a graphics card to this two video signals must be sent from the RAMDAC through graphics cable to the monitor.

That is similar to dual linked DVI which is a single DVI cable capable of carrying two signals to the 2560x1600 monitor. Prior to the development of dual linked DVI ports and cables, 2560x1600 resolution monitors required the use of two "single" DVI cables between the monitor and graphics card.

Therefore, if you want to use the 4th monitor, you will need to buy another graphics card. It can be something as lowly as a Radeon HD 6450.

MEB2003 · Oct 9, 2013

jaguarskx :

The issue is that "Eyefinity" can only recognize up to three monitors. It seems your HD 7870 has 4 ports:

DVI x1
HDMI x2
DisplayPort x1

That is not unusual since that give you the following options for EyeFinity:
1. DVI, HDMI, DisplayPort
2. HDMI, HDMI, DisplayPort

The issue is that most graphic card only has one chip called RAMAC which output video signals to monitors. Each RAMDAC can only send two video signals. Therefore, no matter how many ports a graphics card has, only two of them can be used at any one time.

Cards with DisplayPort has a RAMDAC chip devoted solely to the DisplayPort (to the best of my knowledge). The reason for this is because DisplayPort supports up to 2560x1600 resolution. For a graphics card to this two video signals must be sent from the RAMDAC through graphics cable to the monitor.

That is similar to dual linked DVI which is a single DVI cable capable of carrying two signals to the 2560x1600 monitor. Prior to the development of dual linked DVI ports and cables, 2560x1600 resolution monitors required the use of two "single" DVI cables between the monitor and graphics card.

Therefore, if you want to use the 4th monitor, you will need to buy another graphics card. It can be something as lowly as a Radeon HD 6450.

Okay. I happen to have an extra video card laying around. Didn't know that you could run two different cards at the same time. Thought they had to be the same type. Good to know.

MEB2003 · Oct 9, 2013

jaguarskx :

The issue is that "Eyefinity" can only recognize up to three monitors. It seems your HD 7870 has 4 ports:

DVI x1
HDMI x2
DisplayPort x1

That is not unusual since that give you the following options for EyeFinity:
1. DVI, HDMI, DisplayPort
2. HDMI, HDMI, DisplayPort

The issue is that most graphic card only has one chip called RAMAC which output video signals to monitors. Each RAMDAC can only send two video signals. Therefore, no matter how many ports a graphics card has, only two of them can be used at any one time.

Cards with DisplayPort has a RAMDAC chip devoted solely to the DisplayPort (to the best of my knowledge). The reason for this is because DisplayPort supports up to 2560x1600 resolution. For a graphics card to this two video signals must be sent from the RAMDAC through graphics cable to the monitor.

That is similar to dual linked DVI which is a single DVI cable capable of carrying two signals to the 2560x1600 monitor. Prior to the development of dual linked DVI ports and cables, 2560x1600 resolution monitors required the use of two "single" DVI cables between the monitor and graphics card.

Therefore, if you want to use the 4th monitor, you will need to buy another graphics card. It can be something as lowly as a Radeon HD 6450.

Okay. I happen to have an extra video card laying around. Didn't know that you could run two different cards at the same time. Thought they had to be the same type. Good to know.

jaguarskx · Oct 10, 2013

As long the driver supports the card, then you should have no problems. For example, if you have an old Radeon x1900 graphics card lying around, then you might have issues since AMD dropped support for those cards a few years ago. The newer it is the better.

If you have a nVidia card, then you should be able to have Radoen and GeForce drivers installed at the same time as long as you have Windows 7. I believe Win 8 also allows you to do this as well. Win Vista does not allow you to have both Radeon and GeForce drivers installed at the same time from what I can recall.

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