Disabling external monitor on radeon fireGL-T2 (Thinkpad r50p)

[Hamie]

I have a thinkpad r50p using xorg 6.8.2-rc3 and noticed while looking 
for reasons why my battery only lasts a little over an hour, that it 
always has the external monitor port enabled & running... (Even when 
suspended BTW).

Plugging a monitor in shows the LCD image on the external LCD. Using 
Fn-F7 on the thinkpad seems to turn off the external diskplay, but since 
there's no feedback as to whether it's actually running or not, I want 
some way to actually disable & turn off the hardware associated with 
driving the monitor port itself (Turning on & off on the fly would be 
cool, but just disabling it in xorg.conf would be a bonus).

I've googled & searched the xorg wiki, and there's lots of queries on 
how to get the external port working in various configurations, but 
nothing that seems to indicate how to disable it to save power...

Anyone know? Is there a good description somewhere of how to do this?

TIA

Hamish Marson.