pccard modem unable to allocate fast interrupt

[Ben Kaduk]

Hi all

I have an IBM pcmcia data/fax modem (US Robotics technology) -- "V.34
33.6 Kbps/56 Kbps with XJack Connector" that probes in dmesg as sio4. 
However, the scan also yields the following message:
sio4: unable to activate interrupt in fast mode -- using normal mode

which seems to come from src/sys/dev/sio/sio.c, indicating that my
modem supports INTR_TYPE_TTY but not INTR_FAST.  What is the
significance of INTR_FAST, and could its absence cause any
difficulties in using ppp?
I don't really want to do much research at the moment since I'm on
dial-up, and I don't have local access to the src tree, only the
cgiweb applet. (Incedentally, my problem with ppp is that after
entering username and password, I get some info, such as an IP
address, but ppp does not return to a prompt -- it seems to hang; this
happens at 115200 and 38400 baud (or the recommended values near those
if my memory fails me), so I don't think it's a speed problem)

Sorry I don't have more info about the modem, but since WinXP can't
mount ufs, I don't have a good way to get, say, dmesg or pciconf
information about this card.  The numbers on the outside of the card
are:
10661AS723YF
IBM Modem FRU: 04K0054

Googling these didn't reveal anything terribly helpful, though it
implied that this chipset was actually a winmodem, which would be
surprising.

Thanks

Ben Kaduk