Subject: Re: serial ports
To: None <dgilbert@jaywon.pci.on.ca>
From: Gordon W. Ross <gwr@mc.com>
List: port-sun3
Date: 05/02/1996 10:54:59
> Date: Wed, 1 May 1996 22:15:44 -0400 (EDT)
> From: David Gilbert <dgilbert@jaywon.pci.on.ca>

> Gordon> The 3/50 has trouble keeping up with the serial ports even at
> Gordon> 9600.  Once I finish making H/W flow controll REALLY work
> Gordon> (drop RTS when the input silo becomes nearly full) then it
> Gordon> should at least work without dropping input, but will
> Gordon> probably still be slow on a 3/50.
> 
> 	I thought that this was a hardware limitation.  Are you saying
> that there is a way to make this work... or is this and
> ultra-high-priority interupt?

The zs chip interrupts at level 6 (yes, "ultra-high-priority" 8^)
but that is only for "silo" I/O, and a software interrupt is used
to move the data up to the TTY layer.  The current driver suffers
because there is no flow control to prevent silo overflow.

I think I've got that fixed, but the code needs more testing.

Gordon