Hi Mira,
is it a 1st Gen or 2nd Gen?
I've got a 18i20 2nd Gen, -n 2 -p 128 works with my outdated Athlon
and now with my Celeron without issues. IOW even my new machine hasn't
got much horsepower.
If irqbalance should be enabled, disable it. Did you already test
different USB ports?
What's the output of
/path/to/rtirq status
?
The path were rtirq is installed unfortunately isn't the same for all
distros.
/etc/init.d/rtirq status
/etc/rc.d/rtirq status
or just /usr/bin/rtirq, if so you could run
rtirq status
What kernel are you using?
uname -a
Regards,
Ralf