dual Radeon graphics cards and Xrandr 1.4

[J. Hart]

I have two old Radeon HD 4850 graphics cards in a 4 head monitor 
configuration I'd like to get working with Xrandr 1.4 if possible. I 
built my linux system entirely from source code, so I am not using any 
particular premade linux distribution. I am presently running linux 
kernel 3.14. The X11 system (Xorg) is also built entirely from the 
latest release source code (no prerelease), and so is post-"xorg 7.7". 
(Xorg 7.7 is the latest Katamari release - June 6, 2012).

I am using the following :
Mesa 10.6.5
randrproto 1.5.0
libXrandr 1.5.0
xrandr 1.4.3
xf86-video-ati 7.5.0

The two Radeon cards have a crossfire cable connected between them. They 
are presently working well in a 4 head Xinerama configuration using the 
open source driver listed above (xf86-video-ati 7.5.0)

I have tried starting X without any xorg.config files so that Xinerama 
is not in
effect. After starting the X server, I did the following:

xrandr --listproviders # saw two providers
xrandr --setprovideroutputsource 1 0
clear;xrandr | grep DVI # saw only DVI-0 and DVI-1

The others should have been DVI-2 and DVI-3, but they do not appear in 
the report. Any ideas would be most appreciated.