Hate to drag out this non-pic topic, but there's been a lot of
misconceptions mixed in with good information on this subject.

PC's themselves can handle any number of com ports (I've run 12-16
"non-intelligent" boards on one machine.  Windows 3.x standard com
driver will not allow IRQ sharing or higher numbers of ports.  Many
aftermarket drivers overcome this.  Win95 and NT handle all the ports
you could need.

IRQ Sharing.  Win 95 and NT allow IRQ sharing (meaning two ports IN
USE at the same time on the same IRQ).  HOWEVER - your port MUST have
special hardware to support shared IRQ's.  Most off the shelf modems
& ports don't.  Many boards headed for industrial applications do.
IRQ sharing works well and I generally recommend it.

Win 95 and NT have pretty much solved most of the dos/win3.x com
problems of the past.  With the correct hardware and an understanding
of how things work there shouldn't be any problems.  Granted this all
comes with a bit of overhead (to say the least) but Pentium machines
are cheap.  If you are running multiple ports with little buffering
an no handshaking, just buy a fast machine.

Bottom line isn't too bad.  Good hardware supports shared IRQ's,
'95 and NT support it also - just be sure when you buy that your com
boards support and address and any IRQ, and hopefully shared IRQ's.
(Note that most industrial board suppliers support this stuff,
ourselves included at (shameless plug) http://www.bb-elec.com

Also - the aim of USB (universal serial bus) is to clear this stuff
all up for the user, and from what I've seen so far, it looks pretty
good, although more complex for peripheral mfgs.  I just returned
from the USB Implementers Forum and there is a lot of effort going on
to make sure that it is done right this time.  Looks good so far,
we'll see in the next few months.

-mike
mfahrion@bb-elec.com
At home