[na-user] Dell / Windows 98 / Multiport cards

Dick Green Dick Green" <dick.green@valley.net
Wed, 1 Sep 1999 03:20:51 -0400

>  On other hand, NA does not support IRQ sharing (neither does CT -
> TRLog will because it does not use IRQs at all, but polls the COM ports,
> is why TRLog is limited to 4800 baud).

I was afraid of that. The problem is that modern Windows PCs just don't have
enough free IRQs to support multiple COM ports without IRQ sharing. What
used to be extra IRQs now get used for sound, video, USB ports, network, IDE
ports, etc. Here's a typical example from Dell:

1 - Keyboard
2 - Programmable Interrupt Controller
3 - USB
4 - Comm1
5 -
6 - Floppy
7 - LPT1
8 - CMOS Real Time Clock
9 - Audio card
10 - Video card
11 - Network card
12 - Mouse
13 - Numeric Data Processor
14 - ATAPI
15 - ATAPI

It's amazing that they absconded with IRQ 3 for the USB port -- that used to
be reserved for COM2 and COM4. As you can see, there's one free IRQ (5) that
can be used for a COM port. I can squeeze another one out by deliberately
configuring a conflict with the LPT IRQ (seems to work OK on my present
system.) Unfortunately, I happen to have nine serial devices -- a modem, a
packet modem, two Yaesu rigs, a DCU-1 rotor, an 87A amp, a telescope, a
weather station and a RTTY PTT port. I wouldn't mind adding a serial
controller for my second rotor, too. I've also got three LPT devices -- a
printer, a 2-radio switch interface and a digital camera for the telescope.
My current system came with two COM ports and I was able to add a card with
two additional serial ports (resulting in COM1-COM4 using IRQ 3, 4, 5 and
7), and an LPT port (resulting in LPT1 using IRQ 5 and LPT2 not using an IRQ
at all.) I still need three switch boxes to be able to use everything. It's
a hassle.

Windows 98 will support an 8-port card set up to share IRQ 5 in the Dell,
but NA won't support that. My only choice with NA is to use a non-sharable
2-port card and configure the COM ports with separate IRQs -- either 5 and 7
(deliberate conflict with LPT1), or 5 and 3 (disable the USB port). Since
the Dell has only one COM port and one less IRQ to work with, this means I
lose a COM port when I upgrade to the new system. So either I limit myself
to three COM ports or switch to WriteLog (yuk) so I can configure 8 or 9 COM
ports. Not a happy choice.

Since I don't use the DVP, it sure would be nice to have an INT 14 option in
NA. In fact, we had that option in our comm software back in the old days
(did I mention that I owned a data communications software company a while
back?) We did that specifically to support both kinds of multiport cards --
those with IRQs configurable for each port (accessed via direct I/O) and
those with one shared IRQ (and a DOS driver to utilize it.) Typically, the
vendor-supplied drivers don't have the speed and buffering limitations of
the standard DOS INT 14 COM driver, and might work with the DVP card. I'd
highly recommend this approach.

As an aside, I'm kind of surprised that NA works so well in a DOS window (at
least with two rigs -- I don't use it with packet.) When you do direct I/O
under DOS, there's a danger that you'll have interrupt conflicts with the
Windows COM driver. I was unable to run CT that way -- it would always lose
interrupts from my rig unless run in DOS stand-alone mode. NA must link the
interrupt vectors more intelligently (or maybe I've been lucky.)

I'm sure someone out there will recommend that I just get a second cheap PC
for contesting. Sorry, but I don't want to do that. My shack and home office
(I work at home) are one and the same. Space is limited and I want to have
one computer for everything. I really should be able to do that.

So how about it, Dave? Can you give us the option of using your old INT 14
driver? Or perhaps it's time to bite the bullet and port NA to

73, Dick WC1M

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