Patch-ID# 100051-01
Keywords:	ring serial i/o io input port buffer overflow
Synopsis: Ring buffer overflow msgs from serial port input.
Date: 09-Feb-90

SunOS release:
	4.0.3c

Bug ID's fixed with this patch:
	1029735

Patches which conflict with this patch:

Architectures for which this patch is available:
	sun4c

Obsoleted by:
	4.1

Problem description:

	When running on the console directly (ie, not in sunview), any
	substantial amount of I/O through the serial ports when for example
	running tip, periodically loses data and displays the messages:

		zs1: ring buffer overflow
		silo overflow

	The problem is caused by the kernel running at a high priority (to
	repaint the screen on scrolls) for too long, and locking out incoming
	characters.  This causes the ring buffer message, and attempting to
	print this error causes the silo overflow.  The new kernel module
	provided adjusts the CPU priority correctly to avoid this situation.