About the Drive E:
This is the RAMDISK on the Enterprise.
On expanded machines in a EXOS compatible mode can be support this, especially because the SymbOS only support 1MB memory, on 1MB+ machines lot of free memory for RAMDISK
It is standard FAT volume, at the boot sector from 100h- stored the segment numbers (each 16K) where the RAMDISK stored. Easy to calculate from LBA sector number the memory location where the sector stored.
The loader program can ask the RAMDISK for the SymbOS driver: get the boot sector of the Drive E: and if succesful then get the first segment number from the boot sector at 100h, and this segment number passed to the RAMDISK driver.