[tangue]

Windows CE was loaded from the disks and was an option for developers. The dreamcast had another os which were more close to the naomi arcade machine

[naraic0o]

The article claims that the hardware contained no "OS" and that all discs were self-contained full-linked OSes.

[tangue]

There was a rudimentary os when you boot without gd-rom. It allowed you to set settings, manage memory cards etc I suspect it was loaded just in case where there were no os on the gdrom inserted otherwise the system will boot on the gdrom os. Edit : video link https://m.youtube.com/watch?v=5L9p_Bq_hFk