bit set. I broke stat_imask in Dec 1994 and update_intr_masks() has
copied the breakage to intr_mask[8] since Mar 1995. This can cause
the RTC to stop interrupting in rare cases (under loads heavy enough
for a new RTC interrupt to occur at a critical time just before Xintr8
finishes handling the previous one) and may have caused worse problems.
bf7141134e