Does "nousb" really work?

I've been trying to get a USR 5610 hardware hardware modem working, as can be seen in another thread in the Networking forum. I now believe that the problem is an irq/boot-time problem, so I've moved over here.

On this box, XP reports that the modem and the USB controller both use irq 23. XP is able to use the modem just fine.

I installed RedHat (don't know which version, but I just bought it at Fry's a couple weeks ago so it's pretty recent). RedHat's modem config wizard found the modem just fine, and lspci showed it using irq 5 (NOTE: not 23). When booting with default options, RedHat will hang when setting up the USB controller. If I give the "nousb" boot option, I can boot RedHat, and the modem works (I can get a PPP connection). I wrote down the output of setserial -G so I could reproduce the config in Knoppix.

On my Knoppix HD install, I booted with nousb, did the setserial command that I got from RedHat, linked /dev/modem to the device file (which happens to be /dev/ttyS4). No dice: kppp and wvdialconf still don't detect the modem.

I also tried disabling USB in the bios setup. The irq reported by lspci -v moved from 5 to 6. I changed my setserial command accordingly, but no dice. I also tried booting with nopcmcia noscsi alongside nousb, with the same result.


Any clues?