On the section on the 9825 it says:
[The 9825T] also has a large warning label on outside
top warning the
user not to install any ROMs other than the 98211 Matrix ROM or the
98217A Flexible Disk Drive ROM. It says that installing any plug-in ROM
that is already built into the calculator may damage the machine. I
have never seen this warning on ANY other HP machine.
Actually the HP Series 80 computers also have a similar message (to the
effect that installing multiple copies of the same ROM could damage
the machine).
**vp