SUMMARY: ring buffer overflow - my mouse now is sporadic

From: Steve Poulsen (
Date: Wed May 20 1998 - 10:18:26 CDT

Thanks for the responses. Basically, my system was working too hard. I had
unplugged an unused network connection (two on this machine) and somehow it
was causing problems. I used "ifconfig le0 down" to take care of the
problem and all worked after that. Thanks again.



No Remedy, but a Clarification: zsN is one of the Motherboard's serial
Interfaces, one of which the Mouse is hooked up to. Check your zs
Manpage to be sure about it being zs3 or not.

Ring Buffer Overflows mean that the incoming Data was not read out of
the Interface Chip (i.e., by the CPU) fast enough. Maybe something's
hogging your CPU?


Caused by data coming into the serial port (zs3) too quickly, hence the
mouse behaving erratically. Nothing to worry about unless you mouse is


Is your network co­ax by any chance?????

We had the same problem a few months back and put the problem down to the
network­ less tan perfect trancievers, cables and generally the network not
being up the job for Ultra's...


} Yesterday I started getting messages to the effect of:
} NOTICE: zs3: ring buffer overflow

  I got one on the console. zs3 is either the serial port or the
  keyboard. I suspect something else locked up, and the keyboard buffer
  overflowed. I remember I was using a lot of resources for something
  at the time. (Can't remember what.) Find out what's using resources
  (use top and/or vmstat and/or proctool) and find out why it's not
  letting you have any...

} in /var/adm/messages. At the same time, my mouse has become sporadic. It
} will freeze for less than 1 sec, then make a big jump. Impossible to use.

  The mouse uses the keyboard socket ­ so probably uses the same input

} I am running Solaris 2.5.1 on an UltraSparc.

  I'm running Solaris 2.6 on a SPARCstation LX ... (Lucky me!)


as far as i remember, this problem is explained in one of the many FAQ's
that you can find in the inernet... Try these locations:­stuff.html

I hope, this helps.


Check your mouse and keyboard connectors.

zs3 is the hardware buffer for the mouse port. The only way to overflow
it is usually to move the mouse around while the operating system is
halted (Stop­A, move mouse, go).

It could also be a bad mouse. Perhaps it needs a tail (cord) transplant?


Did you connect anything to the serial port?? Usually that is the cause for
the problem.


Have you applied the recommended patches?


Here's what Sun has to say about this error message:


DOCUMENT ID: 2055­01

SYNOPSIS: Error message: "zsX: ring buffer overflow"

OS: Solaris



TECH AREA: Drivers


KEYWORDS: Zilog zs ring buffer overflow


Occasionally the system console will display the following message:

zsX: ring buffer overflow.


The serial ports on a SPARC system are driven by a zilog 8530 chip.

This is driven by the zs device driver.

The driver maintains a ring buffer for characters it reads from the 8530
chip. If this ring buffer is overwritten before it was serviced this
message will be seen.

Bug id 1029735 describes one such situation in which this message may be

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.

This particular situation was seen on SunOS 4.0 systems and was fixed by
patch 100051.




The message is a symptom of your system working too hard; it's not
related to the cause.

Perhaps your system was swapping a lot.


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