SERIAL

From: G7DMS@GB7WRC.#16.GBR.EU

                         Serial port card IRQ mod
                         ========================


If you want to use IRQ5 for COM3 then here's how to do it!.
If you look at your serial card, you will find that the only interrupt lines
connected are IRQ3 and IRQ4.

1) Identify the IRQ3/4 interrupt lines on the edge connector.  Do this in the
following way.  Put the board on the table with the edge connector towards you
and the component side on the table.  I'm assuming that your board isn't
totally weird and has the components on the normal side of the board!  As a
final check, the back-plane and RS232 connector should now be on the left of
the board.  OK so far?

2) Counting tracks on the edge connector from the RIGHT hand end.  The first
and third tracks should probably have thickish tracks leading away from them.
These are probably power/ground rails (mind you the same pattern is repeated
at the left hand end too!).  The 7th and 8th tracks from the right hand end
should have thinner tracks connecting to them.  The 7th track is IRQ3 and
the 8th track is IRQ4.

3) Choose either IRQ3 or IRQ4 and cut the track before it reaches the edge
connector...if you can cut it just where it joins the edge connector, then
that is the best way.  Now (if neccessary) strip back some of the solder
resist (or other coating) on the track...away from the track cut).  Once you've
done that, solder a wire to the (now cleaned) track.  Solder the other end of
the wire to the 9th edge connector which is IRQ5 (from the right again) and
until now should have had no track running to it.  Solder the wire to the very
top of the edge connector...otherwise the board will not push back into the
slot on the motherboard.

4) Now light the blue touch paper and stand well back!  You'll need to set the
board to pretend to be using the IRQ that you've pinched (ie cut).  Once you've
done that it should work first time.

Some final info:

IRQ7 is normally used by LPT1, but if you haven't got an LPT1 (or you can
disable the port) then you can use that for COM4. IRQ7 is on the 11th track
from the right of the connector (two tracks left of IRQ5).  The connector has
IRQ2 to IRQ7 in sequence (and maybe IRQ0/IRQ1, but you can't use those) so if
you can locate IRQ3/IRQ4 then the others should be obvious.  IRQ's above 7 are
on the other part of a 16 bit card.

some components on the board may be a little static sensitive.

Don't get carried away with nylon underwear and synthetic carpets!  Also make
sure that your soldering iron is earthed...at least it shouldn't carry a
charge that way.

This way will work...there are other ways to do this without track cutting,
but that depends on how your DIP switch/jumpers are configured and also whether
you can easily follow the tracks on the board without losing them anywhere.

(source unknown)
No responsibilty will be taken for damaged caused to equipment by anyone
trying this mod, so proceed at your own risk!.