On 15 Apr 98 at 9:13, [log in to unmask] wrote:

> >   Is there any chance you have a COM4 port in this machine?  Many S3
> > chips include emulation of the IBM 8514/A adapter, and this conflicts
> > with the "industry standard" COM4 address range.
>
>         I'm imagining a method to get rid of this inconvenience, which I
> myself have to test: map COM4/IRQ3 into one of the on mobo com ports, and
> your modem or whatever to COM2/IRQ5. Then probably the port addresses are
> not aliased.
>         To check:
>         -With DEBUG test aliasing on COM4 on modem or card:
>                 -i2EA. You will probably read 1.
>                 -i6EA. You will probably read also 1, which shows aliasing.
>         -Now do the change above, and repeat:
>                 -i2EA. You will probably read 1.
>                 -i6EA. If you get a different reading, aliasing is gone.
>
>         I'll appreciate any feedback.

  I don't see where 6EA comes into it.  Maybe you're talking about
something else.

  To quote from one of the many hits when I search the web for "8514
COM4":
> The 8514-compatible mode of the ... video chip uses I/O port
> addresses from 2E0 to 2E8. This will conflict with systems using
> COM4.
  This particular quote comes from a Dell technical advisory, but
there are also diagnostics to detect the conflict, products which
avoid it, and FAQ answers that identify it as a cause of strange
behaviour.  [These do not, however, always correctly explain the
details of the problem.  One I looked at seemed to imply that a
less-featured video driver could fix the problem, and that's simply
not true.]

David G