ISA modem on FC2

[Amadeus W.M.]

I had this old PC (P2 333MHz) which I gave to a friend. It came with an
ISA Motorola modem. Back in the days of RH 5-6 I used to get it to work
using the isapnptools, but then I switched to broadband and I didn't keep
up with modems. It's not a software modem, but it's internal and isa.

Under FC1 I tried to configure the modem from the network configuration
gui, with no success. I did a tail -f /var/log/messages and while the ppp0
interface was being activated I saw ATZ was sent to the modem twice, and
then I got a "Configure script failed" (or something to that extent, I'm
writing this off the top of my head). Error code 8.

I fired up minicom and I can't even send commands to the modem.
The modem is on /dev/ttyS2 and setserial -a /dev/modem shows irq 5.
>From what I remembered, I knew that was wrong: with isapnp I always had to
configure the modem on irq 11. The same irq 11 showed up in windows, so
I'm pretty sure I have to set the modem to irq 11. 

Now under linux, irq 11 was used by usb-uhci. So the questions are,
under FC1

1) How do I tell the kernel to use another irq (e.g. 5) for usb-uhci?
2) What do I use instead of isapnp to configure the modem to use irq 11?
setserial only tells the kernel what irq to use when talking to the modem.

Thanks!