How fast can linux do serial I/O to a Z8530

Paul Flinders (
21 Jun 1997 20:48:57 +0100

How fast can the current kernels cope with serial I/O from devices
with small FIFOs - I'm thinking specifically of a Z8530 which has a 3
character ring buffer.

I seem to recall a comment during a discussion about fast/slow
interrupts that the split was originally in order to be able to get an
8250 to run at 115Kbps - can the current kernels approach (or even
beat) that sort of performance.

I ask because I have a need to route IP packets comming in over three
64Kbps synchronous serial links to a LAN. One option is to use a
couple of z8530 cards and write a linux driver for them (probably
based on the old kiss tnc driver). Na´vely this seems to imply
handling 24,000 interrupts per second which seems a tall order on its
own without considering ppp, routing sending and recieving ethernet
packets and, occasionally, doing disk I/O.

Does anyone have experience with these devices at this speed? Is Linux
up to this sort of I/O load? Should I even be considering doing it
this way?