VIA Chipsets slow down PCI cards

VIAs official patch, Version 1.01

Under the section "Drivers" VIA was offering a patch at its support site VIA Arena for two weeks only. However, the question was "Do you use a Promise RAID PCI card?" If this is so, the patch promises to "increase the burst rate." As VIA did not mention the performance and stability issues found recently, this can only be viewed as an attempt to conceal the real PCI problems. According to VIA the patch works with all versions of Windows. What exactly this patch does is not documented by VIA.

In our lab, however, this patch really makes a difference with Promise cards. With VIAs own motherboard P4XB (P4X266 chipset) burst transfers went up to 113,3 MBytes per second from 90,1 MBytes/s without the patch. We were using the Promise Ultra 133 TX2 for this test. This is the basic version of the adaptor which not offers any RAID functionality. Even there VIAs patch shows its effect.

As given in the pictures above, our Logic-Analyzer again showed what happens: VIA increased the burst length from 24 to 120 blocks of data, before the bus is released. This explains the significant performance increase. George Breeses Patch, on the other hand, only increases the burst length to 32 blocks of data.