Hello Mike, (that's the one who needs an answer)

You installed the card and let Windows figure out how to install it.
The problem as I see it is in the interrupt handlers of the device drivers. I
know little of Win95 device drivers (still), but a lot more about how
interrupts are handled in a 80x86 system.
Sharing interrupts between more devices is well possible, but the drivers have
to be designed to do so. Most drivers just take over the interrupt vector
(modify it to point to their own interrupt service routine) and after handling
that do an IRET instruction, clean up the Interrupt controller, and that's it.
Mostly this is exactly what you want! This makes it possible to just install a
driver that interfaces to the name COM1: and magically the pre-installed one
is gone.. Drivers are designed (they have to) be chained. The last one
installed to that device name does the job, the others are bypassed.
Interrupts are not chained automagically. Sometimes however, one wants to
share the interrupt with an earlier installed device (= devicedriver). This is
your case.
Sharing interrupts means that you (beiing the driver) detect if the interrupt
was generated by your device, if so handle it, and pass the interrupt to the
previously installed handler. That is a lot more complicated.... especially
the control of the Interrupt controller.

What is good advice for you ?
I suspect the win95 drivers alltogether. They are ment for average users, not
for people like you who want to install more than 2 COM port driven devices.
Try to find drivers that are capable of sharing interrupts 3 and 4 between
ports
COM: 1,2,3,4. Of course you can write them yourself.
I did it for MSDOS and WIN311 using Blaise Computing Inc.'s excellent Asynch
Manager. That was some years ago (1993), it worked  under Win3.11 that still
supported MSDOS drivers, but they may have Win95 compatible products by now.
In between you could experiment with the sequence in which the drivers are
loaded... as I explained, a good driver does not monopolize an interrupt, but
shares it through chaining. This has to do with the way the silicon is
arranged on the motherboard, not with the operating system. The bad boy must
go first...
In Win95 - I am no expert still - throw away all your COM ports and reinstall
them one by one, try and keep record. On paper. One gets distracted by
repeated failed experiments.....

Good luck Mike !

To Miguel:

Mike told us he did.

WF AUTOMACAO wrote:

> Mike Watson wrote:
> >
> > Hi,
> >
> > I have a need to operate 3 comm ports on my pc, so bought a
> > standard card that has FDD, HDD, game, LPT and 2 COMs. I disabled
> > the FDD, HDD and game ports and configured the com ports to
> > 3 and 4 using jumpers on the board.
> >
> > Having installed the card, Win95 detected the new ports. All well
> > and good, but in use, com3 stops com1 working and com4 stops com2.
> >
> > It must (surely) be possible to configure the system so that I can
> > use at least three of the ports at the same time.
> >
> > Anyone help me out on this?
> >
> > Thanks and regards,
> >
> > Mike Watson
>
> Are you using differents IRQ?
>
> Miguel.



--
Regards,

Wim
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  Wim van Bemmel, Singel 213 3311 KR Dordrecht
  Netherlands
  mailto:bemspan@xs4all.nl

  ... Life is about Interfacing .....
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