Simulator newbie question

["Mike Motyka" <mikem@pixim.com>]

I'm looking at ISS options for SW bringup of a fairly elaborate SOC. The
CPU will be a 9x6E_S so it looks like the ARMulator supports the
instruction set. Our toolchain is gnu. 
 
I want to have a decent understanding of the architecture of the
simulator before I start adding our stuff. I've done some cursory
browsing of the source. Is there any design documentation for the GDB
simulators in general and the ARMulator in particular?
 
Assuming that there is little documentation to be discovered :) I'll ask
a few questions for the hell of it:
 
The GDB remote protocol is RSP - it's well documented and I assume this
is what the ARMul speaks over the socket it opens?
 
Why are there references to RDP and RDI buried in the ARMul? 
 
Why is the "Angel" debug thingy from ARM in there? Is it present by
default? I need a clean CPU.
 
It looks like armvirt.c is my attachment point for I/O though I'll
probably have to get a hook into the instruction cycle somewhere to
drive even a crude approximation of a timer.
 
All in all it looks like a decent place to start.
 
 
Time is a great teacher, but unfortunately it kills all its pupils.~
Hector Berlioz