I noted DDU at http://www.guru3d.com/files-details/display-driver-uninstaller-download.html (again here) and my bet is something in mixing these old and new is just plain unsupported.
You would have to deal with Nvidia's own support and my bet, they won't fix it given the age of the old 730. Linustechtips has posted videos about mixing like this. The results were either disasters or "didn't work."
Fix? Most likely another 970.
I recently upgraded my monitor setup from 3 monitors to 6th. Unfortunately, I can't get the 6th to work. I'm using a combo of DisplayPort, HDMI, and DVI-D on 2 different GPUs. My motherboard itself doesn't have any video outputs, so the ones on my GPU are the only option. I thought I had the solution after being told that I needed an active DisplayPort to HDMI adapter, being that DVI-D and DisplayPort don't work together (I've been told), but that adapter did not work. Also, I was already using a DisplayPort and a DVI-D on the same GPU and it was working just fine. It's when I try to add the 6th monitor (via DisplayPort, or the DP to HDMI adapter) that the 6th monitor won't work. My main GPU is capable of running 4 monitors at a time, and my other GPU (not running SLI) is capable of running 2. Here's what I have:
The outputs on my computer:
GPU GTX 970:
[3] DisplayPort
[1] HDMI
[1] Dual-Link DVI-D
[1] Dual-Link DVI-I
GPU GT 730:
[1] HDMI
[1] DVI-D
[1] VGA
Here's the inputs on my monitors (all 6 monitors are the same - ASUS VG248QE):
[1] DisplayPort
[1] HDMI
[1] DVI-D
I'm currently using:
On the GTX 970:
[1] HDMI
[1] DisplayPort
[1] DVI-D
On the GT 730:
[1] HDMI
[1] DVI-D
Like I said, I tried a ACTIVE DisplayPort to HDMI adapter (and also a passive adapter, for that matter), and I tried all combinations with different cables, GPUs, etc, and I still can't get the 6th monitor to work. Do I have any other options here? Can I do a DVI-I (from GTX 970) to DVI-D cable? Would that work? There has to be a way of doing this.
Thanks in advance for any help

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