HIPORT by Joe Horn.  Written in Assembly.  Impossibly fast.

--> GX ONLY!!!

Just run it.  HIPORT returns the number of the highest port in
the card installed in GX slot 2.

For example, if there's a 1 Meg RAM card plugged in, HIPORT will
return 9, because that's the highest port number in a 1 Meg RAM card.

If HIPORT returns a 1, that means that there is no card plugged into
slot 2.  It does *not* necessarily mean that there is a card in slot
1.

It is intended primarily for programmers, who can use it like this:

    2  HIPORT  FOR  p  ...  p  ->TAG  ...  NEXT

The size of the card (assuming that it's not a 32K card) can be
obtained in ways like these:

   HIPORT  1  -  8  /       -->  size in megabytes
   HIPORT  1  -  128  *     -->  size in kilobytes
   HIPORT  1  -  131072  *  -->  size in bytes

Thanks to Bertrand Schmitt for telling me the address in RAM where the
port 2 information can be found (see HIPORT.S).

See also SPORT and PORTSTAT on this disk.