How does pre memory C code work on K8.

Something has been troubling me for some time which is how the code manages
to run before the memory controllers are configured. The assembler I can see
has no accesses to memory, but the C code does, is their some magic gcc
switch that makes it be entirely register based?

It's troubled me for a while one the memories up then I'm more than happy
but before that I'm a little bemused.

Many thanks

Chris