Ken Nutsford writes:
>We have an internal modem on COM4 in our Windows 95 Pentium 90 PC. The CIM will
>not dial out to the CIS. Under terminal emulation, the pointer freezes when the
>screen saver kicks in and we have to go into configuration mode to re-activate
>the connection...
>the same effect as the screen saver and we are unable to get at the
>configuration mode to re-activate the connection.
>
>Our PC supplier says MicroSoft acknowledge there are problems associated with
>COM3 and COM4.
 
This sounds like a classic I/O or IRQ conflict, particularly since the
screen saver is involved and may write directly to the video card. There
are a couple of things you can try.
 
1. COM3 and COM4 normally share interrupts with COM1 and COM2. The Win95
   problem might be with this sharing. Try assigning different IRQs to
   your COM3 and COM4, so all four ports have different IRQs. If you
   have a full computer, this may not be easy to do. It's particularly
   helpful not to have your mouse serial port sharing interrupts with
   anything else. I can't find my configuration right now, but I think
   it's something like: COM->IRQ4, COM2->IRQ3, COM3->IRQ6, COM4->IRQ11.
   Not all serial cards will support all IRQ assignments for COM3 and
   COM4.
 
2. As others have mentioned, there might be a conflict with I/O addresses.
   See if your video card setup allows you to change the I/O address;
   some do. Do you have any unusual I/O cards in your machine? You
   can use MSD to find some of this information, but not all. MSD also
   assumes IRQ assignments for some devices, rather than checking them
   (that is, if it finds the device at the expected I/O address, it
   assumes the standard IRQ for that device).
 
3. Buy a Macintosh, from which these problems are absent by design.
   (From someone who's spent HOURS finding combinations of addresses
   and IRQs that allow large configurations to work reliably.)
 
-- Bruce
 
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