Section 4: The 686B bug
4.1 What is the "686B" bug?
In early 2001, it was discovered that new motherboards with the KT133A chipset could damage data that was being copied between IDE hard disks. The problem was narrowed down to the VT82C686B chip on the motherboard. When the computer's PCI bus was busy, any data copied between the primary and secondary IDE buses could be corrupted. In addition, the computer could crash or reboot during this copying.
The problem occurred more often when a Creative Labs Soundblaster Live card was present.
4.2 Does this patch fix the "686B" bug?
Yes, sort of. This patch is a workaround for the problem, not a complete solution. This patch adjusts the PCI bus to permit the 686B chip to deliver more data without interruption, which has the effect of reducing or eliminating the 686B bug.
Please note that this patch has grown over time to solve more than just the problem of 686B IDE corruption.
4.3 Is the "686B" bug VIA's fault?
The problem seems to be the fault of a bug in the VT82C686B chip. VIA has acknowledged the issue and began working with motherboard manufacturers to stabilize motherboards that have the problem.
4.4 Does this patch do something to the 686B chip?
No. This patch changes settings in the chip that is controlling the 686B. This patch does not directly adjust the 686B chip.
http://www.georgebreese.com/net/so [...] qvl019.htm