Help! SCO Xenix/80286 Hardware error

[tony at joshua.math.ucla.edu]

Hello Netland,

We have a problem and I hope somebody out ther can explain it.

My brother upgraded his company's True Blue 6MHz IBM AT with a 12MHz DTK 
80286 motherboard (with the DTK BIOS) yesterday.

He is running SCO Xenix Version 2.2.1 and everything worked fine
until suddenly it gave the following message:

TRAP 00FF in SYSTEM
  ax=0006, bx=B0D6, cx=0000,dx=00A1, si=0080, di=0000
  bp=03BA, f1=0202, uds=0018, es=0018
  pc=0030:3231,  ksp=0394
panic: Trap in system

The system had to be reset so it was not shutdown correctly.
Now every time it tries to do a fsck it gives the "trap" error message.
In addtion logging in as root also induces this trap error.
We looked in the manuals but we couldn't find a hardware section that
explained this error.

The place where he bought the motherboard said the the 80ns RAM chips
made by NMBS that he is using are not compatible with the DTK motherboards.  
Has anyone else ever heard of such a thing?  Can in-compatible RAM chips 
cause this problem?

By the way he has a DOS partion and everything runs fine when its in DOS.

How can he get rid of this trap error?  What may be causing it?

Thanks in advance.


Tony