Cisco LAN2LAN Software

Document ID: 15014

Contents

Introduction
Prerequisites
      Requirements
      Components Used
      Conventions
Symptom
Reason
Solution
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Introduction

This situation has been found to occur with some AST Bravo LC computers that use cache memory.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

This document is not restricted to specific software and hardware versions.

Conventions

Refer to Cisco Technical Tips Conventions for more information on document conventions.

Symptom

System ABENDs (ABnormally ENDs), hangs, or operates erratically.

Reason

Some AST Bravo LC 4/66 computers with cache memory contain cache memory chips that are marginal with regard to timing. This causes the system to randomly or, in some cases, consistently, error. The symptoms are different for each computer, based on the characteristics of each of the individual cache memory chips installed.

Solution

Remove or replace cache memory chips if failures are detected.

AST Bravo LC 4/66 computers with 15 nano-second cache memory chips are known to fail. There have been no known failures when the computer has 12 nano-second chips installed. LC 4/33 computers might have a similar problem, but no testing has been done on this model. In order to determine if your computer has the parts in question, remove the cover from your computer and look at the motherboard. Looking from the front of the computer, about five inches from the left edge and near the front edge of the board, you should see four connectors for DRAM SIMMs (small circuit boards that stand vertically when plugged in) that are marked "BANK0" through "BANK3". Just to the right of the SIMM connectors there should be nine sockets for the cache memory (refer to figure 10 on page 22 of your AST Bravo LC User's Manual). If there are no chips installed in these sockets, the computer does not have an external cache, and you should not experience this problem. If there are chips installed and they are 15 nano-second parts (that is, they are marked xxxxxx-15x), they are suspect and you should run a memory test to verify their operation and/or have the chips replaced with faster parts.

You need to run a fairly comprehensive memory test program such as "CheckIt" to detect any problems --the power-on self-test does not detect failures. The failures occur more often if all four SIMM sockets contain memory. Although, after some time, failures occur with only one SIMM installed. In tests performed at Cisco, with only one SIMM installed, only one or two failures occurred in 99 passes of the 'quick' memory test. With four SIMMs installed, the failure rate increased significantly.

There are two options if failures occur:

1. Remove all nine cache memory chips, disabling the external cache.

2. Replace the eight 15-nanosecond chips. The ninth (20-nanosecond) chip is ok. Contact your computer dealer or AST.

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