Ah, fair. On modern Windows it's really cmd.exe faking it with env vars, not the API. Didn't know NT reserved space for per-drive CWDs and then never used it.
Another Windows oddity: each drive letter has its own current directory. D: doesn't mean the root of D:, it means "wherever you last were on D:". Same with C:foo, which is relative to C:'s current directory. DOS baggage that's still around.
the rom-to-ram bootstrap is a nice touch. after it hands over, what stops
the bootloader from writing to I-SRAM again? a mode flag in the control matrix?