Instead of it being done through a ramdisk, the restore tools seem all to be right there in the OS, This is probably because they originally did restores through userland.
- The iPhone Prototype came with 03.06.01_G
- The firmware dump comes (in /usr/local/standalone/firmware/) with 03.06.00
Flashing 03.06.00 on a retail iPhone can be done with bbupdater, but results in loss of Carrier Network connectivity.
In /System/Library/Caches/com.apple.kernelcaches, there are kernels for other CPUs, such as S5I3000, S5L8900XFPGA and Freescale MX31. This is probably because Apple did not know which one to use at the time, and/or they had different prototypes with different CPUs in them.