M6, RHEL 6.6, unable to connect connect EDID monitor to valid display devices

I am unable to connect EDID monitor to three out of four valid display devices. Originally started with physical pass through from rhel 7.2 KVM to rhel 6.6 guest, then continued with bare metal rhel 6.6 on the same hardware. The bare metal behaves same as the guest. Xorg.log claims DFP-0, DFP-1, DFP-2, DFP-3 as valid display devices. EDID monitor can connect only to DFP-0 but not to the other 3 display devices. I need two EDID monitors connected, hence I need two display devices capable of connecting. I am using 352.79 driver.

[1195357.159] () NVIDIA(0): Option "ModeDebug" "True"
[1195357.159] (
) NVIDIA(0): Option "ConnectedMonitor" "DFP-1"
[1195357.159] () NVIDIA(0): Option "CustomEDID" "DFP-1:/etc/X11/EDID.txt"
[1195357.159] (
) NVIDIA(0): Option "MetaModes" "DFP-1: 2560x1600 +0+0; DFP-1: 1920x1080 +0+0; DFP-1: 1920
x1200 +0+0"
[1195357.159] () NVIDIA(0): Enabling 2D acceleration
[1195357.159] (
) NVIDIA(0): ConnectedMonitor string: "DFP-1"
[1195357.772] (–) NVIDIA(0): Valid display device(s) on GPU-0 at PCI:4:0:0
[1195357.772] (–) NVIDIA(0): DFP-0
[1195357.772] (–) NVIDIA(0): DFP-1
[1195357.772] (–) NVIDIA(0): DFP-2
[1195357.772] (–) NVIDIA(0): DFP-3
[1195357.772] (**) NVIDIA(0): Using ConnectedMonitor string "DFP-1".
[1195357.833] (II) NVIDIA(0): NVIDIA GPU Tesla M6 (GM204GL-A) at PCI:4:0:0 (GPU-0)
[1195357.833] (–) NVIDIA(0): Memory: 8388608 kBytes
[1195357.833] (–) NVIDIA(0): VideoBIOS:
[1195357.833] (II) NVIDIA(0): Detected PCI Express Link width: 16X
[1195357.833] (EE) NVIDIA(0): Failed to assign any connected display devices to X screen 0.
[1195357.833] (EE) NVIDIA(0): Set AllowEmptyInitialConfiguration if you want the server
[1195357.833] (EE) NVIDIA(0): to start anyway
[1195357.833] (EE) NVIDIA(0): Failing initialization of X screen 0

You require the GRID 2.0 drivers (352.70) along with a virtual workstation license for multi monitor support

Tesla driver for M6/60 has single monitor only, both virtualised and bare metal.