Read the following section of the init command man page.
The above is from the 6.0.0 documentation but is backwards compatible to Xenix.
---------- Post updated at 01:14 PM ---------- Previous update was at 01:09 PM ----------
If you are unable to power down the system, because the cmos does not support it, you may be able to create a workaround using a UPS that you can send a "power off in 5 minutes" command to just prior to shutting down the SCO system.