Soft reset button on PowerPC

Hi

I am looking for 'Soft reset' button on Power4/Power5 boxes. Is it the same
as the yellow reset button commonly found on the front panels of these
machines? It will be great if someone can provide me pointers regarding
the location of the button.

On Power5 boxes, function 22 on the Operator Control Panel is meant for
dump triggering. But when I try it on a p520 box running Linux, nothing
happens and the system continues to run. I suspect I am missing support
from the Operating System. Does anyone know how I can enable support for 
this function from Linux?  

I am investigating methods for triggering a dump(Kdump) on hard hang on
stand-alone PowerPC boxes (no HMC, single Lpar), and hence need to figure
out if any of the above methods can be used.

Any pointers will be of great help. Please Cc me, as I am not subscribed 
to the list.

Thanks
Rachita