Trident cyberblade/i1: Rotate does not work

[Markus Heller]

Dear list,

I have an onboard cyberblade/i1 chipset 

01:00.0 VGA compatible controller: Trident Microsystems CyberBlade/i1 (rev 6a) 
(prog-if 00 [VGA])
        Subsystem: Trident Microsystems CyberBlade/i1
        Flags: bus master, 66MHz, medium devsel, latency 32, IRQ 11
        Memory at e4000000 (32-bit, non-prefetchable) [size=8M]
        Memory at e5000000 (32-bit, non-prefetchable) [size=128K]
        Memory at e4800000 (32-bit, non-prefetchable) [size=8M]
        [virtual] Expansion ROM at 10000000 [disabled] [size=64K]
        Capabilities: [80] AGP version 2.0
        Capabilities: [90] Power Management version 1

and I'm using the 7.1.0 x.org graphics server. I want to rotate a WXGA screen 
(1280/720) so that I can display the full length vertically. I'm OK with a 
different screen resolution, but what can I do?

Unfortunately I cannot get the rotation going. The Option line

Option          "Rotate"                "CW"

in the Device section has no effect. 

I'm using the trident driver right now. 

Does anyone have a checklist what I need to consider in order to configure 
rotation?

Thanks in advance!

Markus