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SubjectRe: serial ports
   Date: Thu, 8 Aug 1996 13:05:04 -0400 (EDT)
From: "Andrew E. Mileski" <aem@nic.ott.hookup.net>

I was refering to 2 and 4 port cards like the generic ones you
can pick up at most computer parts desks. I also carefully chose
my words so that what I wrote could be applied to _ANY_ brand.

You said:

>Every 2, 4, and 8 multi-uart card I've ever used or seen has the
>extra logic required for electrically correct ISA interrupt sharing.

I have **never** seen a multi-uart card using the COM1/2/3/4 addresses
that has **ever** had the extra logic required for doing electrically
correct ISA interrupt sharing. And I say this with 10 years of
experience in the PC/ISA "architecture" (if you can call it that without
abusing the term "architecture" too much).

The reason why I reacted so angrily to you note is because I'm tired of
hearing people complain about why they've tried to use COM1 and COM3 on
some cheap $10 (in your words) "generic ones that you can pick up at
most computer parts desks", AND THEY DON'T WORK. I'm tired of sending
the same e-mail messages over and over and over again.

If you use a cheap $20 generic one, in my experience the chances you
will get the interrupt sharing to work is zero. If you get a properly
designed AST FourPort, or a Usenet serial card, or a Bocaboard card,
which are designed to be able to share interrupts, then you will win.
But you have to pay more for a card that's designed correctly.

You _CAN_ share any interrupt. It takes extra hardware. A board
that supports this _CAN_ share IRQ4 between COM1 and COM3.
_BUT_ not all boards have this capability.

Interesting. You said in your original message that *all* boards have
this capability, and this is simply not correct. If your message causes
novices to have hope that they can actually share COM1 and COM3 using a
"generic COM 1/2/3/4 serial port", you will have just increased the
amount of work I have to do --- because I feel I have a responsibility
to help out newbies who send me e-mail asking for help --- and I don't
have the time to deal with this nonsense.

Please don't spew mis-information, while sounding authoratative. Those
people who sound like they know what they are talking about really annoy
those of us who do. :-)

- Ted


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