Shortly after NAMM an updated version of our Tech Info \'USB kills audio\' will be uploaded to the website. Here is the most important information:
In the last weeks we have done many comparison tests, and were able to track down the real cause behind the effect of USB-caused distortion at low latency: it\'s the well-known Intel BX-chipset!
The contained USB controller 82371AB hogs the PCI bus, in case (as already described in the Tech Info) the Bulk transfer mode is used. BUT: this is only true for older BX-based motherboards, like the Asus P2B series, or the popular P3B-F. To be more precise: it only affects BX-boards that have only 2 USB ports!
On all newer boards having more than two USB ports the hogging no longer occurs, even when using the BX chipset (for example Asus CU-BX). It seems the additional hub de-couples the controller, or changes the way it is used.
This also shows a simple solution for all owners of older boards, how to solve this problem: simply get yourself a (cheap) USB PCI card, and use its USB ports instead of those on the board.
According to our tests boards with Intel\'s i815, VIA\'s KT133 and 694 also work problem-free in critical USB usage.