[ale] configuring getty for dialOUT logins

dZothMuellarg zot at crl.com
Mon Aug 5 12:24:15 EDT 1996

^The Wayward Mage wrote:
^> > Well, my interrupt was right, also; it was just being used by two
^> > devices. This works as long as only one of those devices actually
^> > generates interrupts.  And the behavior was erratic; sometimes I
^> > could get the data from the terminal to the Linux box, and sometimes
^> > I couldn't. That is, it worked some of the time. The point is that
^> > the interrupt can be "right", but there can still be an interrupt
^> > conflict, and then you might see the kind of behavior you describe.
^> How can I found out if this is the problem?  What may be using the same
^> interrupt?

If you ever install a card, you should write down, in a note book,
all of the interrupts and port address (and DMAs).  You should never
install a card without considering this first.

^> Michael
^Don't look at hardware conflicts until you're really, really
^sure the software is right (i.e. by hooking it up to a different
^machine and getting it to work right the first time with the same
^software configuration) - hardware conflicts are a huge pain in the
^ass to diagnose.

I disagree.  Hardware conflicts are more preventable than software.
You should know ahead of time though.  Once in, they are easy to
suscpect but hard to ferret.

Most hardware conflicts will still let you operate a little bit (even
if to get errors)

[good advice deleted]

^There are supposed to be programs that run under DOS that tell you

In the PC repair curse I teach, I tell people this will help, but not if
you don;t have the program :(  I usually reccomend learnig how to
figure thin things out using dos tools.  Under Linux I use linux tools.
For instance:

  seterial (IRQ, port "believed").
  Minicom (CHange values quickly, can get partial results)
  ipconfig (beleived ports, etc.)
  /var/adm/messages suprising wehat the kernel will tell you, esp for netcards

^There's an important fact to be aware of wrt PC serial ports (the
^built-in ones): COM1 and COM3 _always_ share an interrupt (usually 4),
^and COM2 and COM4 always ahare, usually IRQ 3.

Not true.  They _default_ to those settings, _usually_.  Even cheap $10
I/O cards allow you to change the IRQ for the com ports.  The kicker is
usually cheap modems or serial mouse cards (MS).  Sometime old I/O cards
will not let you move the IRQs, but I have regularly had 4 or more
Com ports in a system.

^I hope you find out that the software is really the problem, before
^you have to get into all this :-]

I hope other people check first, in the future :)

In reality though, an IRQ share only collide when both devices send an
interuppt, i.e. they are both recieving something.  Thouse a mouse and
a modem ca share an IRQ, until the modem recieves something, and you
move the mouse.  Under windows this can cause the serail communications
to stop working, until you nmove the mouse, amuzing in periods of low
stress.  The lower IRQs are usually available:

3 [com2]
4 [com1]
7 Printer, but the printer rarely IRQs, and you can usually disable this.  I always do,

10 Your net card is proably in 10 or 11

I'd have to look up the rest, but there are a couple of other IRQs that
may be availble.

The port addresses cannt be shared very well at all.  Often the kernel
will bitch loudly if you try.  And DMAs are rarely a problem.  I am not
sure why, but they seem to conlfict less often (I know SB has a nice
setup program, perhpas it tests well).

ZOT                                                        zot at crl.com
Home Page:   http://www.crl.com/~zot/home.html
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