[Techtalk] About to go insane over Modem Problem

[PCasper]

I've gotten Debian installed... haven't touched the firewall yet 
because.....

it won't find my modem.

Modem worked fine in Mandrake, although it  did so by curling up and 
purring happily on /dev/ttyS5, which seemed strange to me, but it 
worked, so I wasn't going to argue.

Debian doesn't install /dev/ttyS5.

I've tried using setserial to convince my modem that /dev/ttyS2 or 3 
would be good... after all, windows thinks the modem is on COM3, which 
should be /dev/ttyS2 in linux.

No worky

Modem is a USR Performance Pro internal PCI. It's a hardware modem. 98% 
of the "configuring modem" sites I find through Google assume you're 
starting with a WinModem. I'm not.

I have recompiled the kernel, added multiple serial port support, made 
sure it still support ppp. Thankfully, it runs and I don't think I broke 
anything else in the process.

setserial will assign the IRQ to whichever ttyS* I attempt to assign. 
I've been exercising the highly scientific method of guessing at the 
UART to assign using setserial. However, when I attempt to assign the 
memory address used by my modem (0xe400), it tells me that the address 
is already in use and won't assign it. Yet I know of no way to check the 
memory address and see what serial port has assigned itself to that 
address (which would, presumably, tell me what serial port my modem has 
determined that it likes, which should solve the whole problem)

I've tried running
/usr/sbin/chat -v -t 5 '' AT OK </dev/ttyS3> /dev/ttyS3
Which produces the error in my ppp log "Can't get terminal parameters. 
Input/Output error"
Notably, running the same string for /dev/ttyS2 simply times out without 
the error - which means, I think, that I should be focussing on ttyS3 
for my modem. I've googled for the error message that I'm receiving, and 
found a handful of references... largely people who've asked the same 
question about the same error. There's very little in the way of 
responses - either no-one responded or responses were made privately, 
not on the same mailing list that the question was asked.

I'm sdtumped. No idea what I'm doing right, what I'm doing wrong, or 
what needs to be done. In nearly every other way, I'm happier with 
Debian than I was with Mandrake... I got a decent clean install, very 
little running that shouldn't be running, etc etc. But if I can't get my 
modem working, it's pretty much a useless exercise :-(

Any thoughts, help, links, WMDs, etc, would be appreciated. Thanks folks!

--Poppy