RH EL5 dual monitors spanning display support

[Chiu, PCM (Peter)]

Hi,

I am trying to get RHEL 5 to display on two dual Dell 2407WFP monitors
in spanning mode but without success.

The hardware is a Dell Optiplex 745 with ATI X1300 PCI graphics
controller.
There is only 1 DVI connector on the ATI X1300 controller, and the two
Dell monitors are connected using a Y-piece cable.  The ATI X13000 spec
did indicate the support of two monitors with independent resolution
controls.

With the system-config-display configurator, the standard RHEL 5 does
not recognise 
the ATI x1300 controller, but reports it as ATI unknow device 7183.  
It then uses vesa device driver.
The two monitors display as a mirrorred set, even with dual head
selected.

With the ATI-driver-installer-8.36.5-x86.x86_64.run, the fglrx driver is
loaded,
and it gives occasionally 1900x1200 resolution, but often falls back to
1600x1200 mysterously.
Still, the two monitors are displaying as a mirror to each other.  Did
try to invoke
aticonfig --initial=dual-head, but not much joy.

Wonder if anyone has got any joy/idea on this?

Thanks.

Peter