Mike Watson wrote:
> 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.

As you're probably aware, Com1 and Com3 share the same interrupt, as do
Com2 and Com4.  I've always found that my internal modem works well when
sharing the irq with my mouse.  My configuration is:
  Mouse: Com2
  Modem: Com4
  Other: Com1
In my case, "other" is a switch box to switch between my PIC-Start plus
and my datalogger.

Another problem could be that Win95 assigns interrupts, so one of your
Com ports might be mapped to IRQ5 (for example).

To check out your Win95 settings, do the following:
 1. Right click on "My Computer"
 2. select "properties"
 3. select "Device Manager" tab
 4. open "Ports"
 5. select a port, push "properties"
 6. select "Resource" tab.
 7. repeat 5 and 6 for all ports
For a "standard" (pre-Win95) setting, you should see
 Com1: I/O 03F8-03FF Irq 04
 Com2:     02F8-02FF     03
 Com3:     03E8-03EF     04
 Com4:     02E8-02FF     03
If you don't have the above, unclick "Use automatic settings" on the
rsource tab and set them to the above.  This _should_ be safe because it
is unlikely that Win95 selected any of these settings for other devices.

::Matt