I have a quin-head rig:
Radeon X1900XT 256MB PCI-E (2x Dual Link DVI)
Radeon 9250 128MB PCI (1x DVI, 1xHD15)
Radeon IGP1150 (onboard X300, 32MB shared, 1xHD15)
The rig is a Sempron 3000+ with 2GB Corsair XMS3200 (4x512) on a Giga-byte mobo.
I only use all heads when in 2D, in 3D I only use the primary screen on the X1900XT.
The screens on the X1900XT are always near-perfect ... the screen on the IGP1150 is adequate, but the screens on the 9250 are very laggy in 2D -- e.g. if I drag a window around I see it redraw approx twice a second, whereas on the X1900XT the movement is perfectly smooth.
I've checked ATI's (or should I say AMD's?) site for driver updates and realised that the 9250 is no longer fully supported in latest Catalysts and that older Catalysts should be used for such BUT I can't have both and thus need some other way of resolving the performance issue which I believe to be driver related, yet I need newer drivers to ensure that the primary screens display well, especially if playing a game.