Crash Test: Problems with VIA's KT133/KT133A chipset 1/2
Version 2.11, July 19th, 2001
Zur deutschen Version: Crashtest: Probleme mit VIA's KT133/KT133A Chipsatz
The VIA 686B Southbridge
High PCI-traffic due to the use of sound-, tv-, videocapturing-cards or NICs, causes data loss on the VIA 686B southbridge which is used with the VIA KT133A/KT133 chipset. The problem will occur especially on computers using a Creative Labs Soundblaster Live! soundcard. When the CPU waits for 3 busmaster requests until it accesses the bus itself a buffer might overflow and data will be lost. VIA offers a patch that will allow the CPU to wait only for 2 requests preventing the overflow and data loss. This patch might affect audio- and videostreams which will have dropouts due to the minimized bandwith. Since the IDE-controller of the 686B is affected by the data loss it is a serious problem. It is rumoured that a new revision of the chipset has been released to fix the problem.
Rumours all arround!
Thanks to John Gatt - who works for VIA Australia in Marketing - there are a lot of rumours in the www and print media. He said that there is no bug and we caused it by playing arround and overclocking our systems. John Gatt's problem is that VIA takes us and the problem more serious than him. VIA was not at all amused about John Gatts comments. Make a printout of the interview above if anyone quotes John Gatts.
The VIA's KT133A Northbridge
If your northbridge is affected and you are using an AMD Athlon-C CPU (with 133/266MHz frontsidebus) the mainboard will hang while performing a warmstart. Only 20% of the chips with the productcode 1EA0 or 1EA4 will cause this problem. If you have the problem set your frontsidebus to 100/200MHz. When the problem is gone you most likely proved your northbrige to be buggy. To solve the issue set the I/O voltage from 3.3 to 3.45 volts. Contact the mainboard manufacturer - you might get the board replaced.
The mainboard manufacturers offer updated BIOS versions and VIA included a patch in the v4.31 driverset. We have a list ready for you, if your mainboard manufacturer is not listed you should type in their website manually and have a look for an updated BIOS yourself.
If you don't have a Creative Labs soundcard in your system, we show you how to fix the bug on your own without VIA's help: Bugfix for everybody.