It seems that the printer driver causes an incredible number of interrupts
   per seconds, thousands of them.  Probably as many as your machine can
   handle.  You should try the interruptless driver, but what is really needed
   is for someone to fix the ltp driver, perhaps to use DMA.

I have been trying the interruptless driver, but it goes incredibly
slowly.  Like a line a minute or something.  I was thinking of
switching to the interrupt driver, but now I'm not so sure that will
help.

What am I doing wrong?

Cheers,
Brook