Jason Thorpe:

> Note that TTY => NET => BIO assumes a "level" interrupt scheme, where the 
> i386 uses a mask.  Because of slip/ppp/strip, TTY has to block NET.  The 
> masks are calculated at run-time based on which devices ate attached to 
> which IRQs.  Now, if your 3c509 shares the IRQ with your serial ports, 
> NET will also block TTY, which could lead to lossage.

Well, this isn't the case on my system.  All things have their own IRQ's.

But this reminds of another problem: I am setting up a 486/33 for a
customer.  The machine has a 3com509 which suffers from - guess what?
yeah, overruns.  Using ftp to transfer files to the 486 from a Sparc
is very slow - transfer speed is less than 100 k/s.  I guess this could
be the same problem as the one with com.c - disabling the interrupts
for long periods of time.  (My A3000/Hydra has the same Ethernet
problem, btw).

> I think there are some IRQs which do have priority as far as interrupting 
> the CPU ... but I'm not sure of the heirarchy.

Is there an easy way to monitor the interrupt levels on the system?
Haven't got a logic analyzer..

  -jm