Marcus,
I think there is a misunderstanding here -- Adam's question was why is the number of the chief task a part of the thread-id data structure (l4_threadid_t). As it would be beneficial to move from 64-bit thread ids to 32-bit thread ids on 32-bit architectures like x86 and StrongARM, Adam is looking for ways to reduce the size of the thread-id data structure, and one way to do so would be to throw out the chief number.
Personally, I don't think there is a real reason to keep the chief number in the thread id except for backward compatibility and for ease of porting L4 apps to a changed ABI.
L4 has inherited this data structure from L3, and I would be interested in why the chief number ended up in the thread id in the first place. Jochen?
Michael
l4-hackers@os.inf.tu-dresden.de