Specifications

46837 Rev. 1.0 March 2010
SB700 Family Product Errata
Product Errata
9
8 USB 1.1 ISO OUT Devices May Not Function Properly
Description
The audio from a USB 1.1 ISO out device (e.g., USB speakers) may be corrupted when both the A-Link power
saving feature “PLL power down mode” and the L1 link power management feature are enabled. The PLL
power down mode is a power saving feature that is optionally enabled for mobile systems. If both L1 on the A-
LINK interface and the PLL power down feature are enabled, the USB controller may encounter increased
delay in fetching the data from memory. The USB 1.1 host controller will pre-fetch the data only for ISO type
devices to compensate for the delays when fetching the data from the system memory. The increased delay
due to PLL power down mode enabled (> 5 µS) will cause the internal logic to not latch the pre-fetch data
correctly and cause data to get corrupted in the pre-fetch buffer. If only L1 on the A-LINK interface is enabled
then there will not be any audio corruption.
Potential Effect on System
Due to this data corruption, occasional sound corruption may be noticed with the USB 1.1 ISO out devices
connected to the host controller.
Suggested Workaround
A USB filter driver will be required that will disable the PLL power down mode if there is a USB 1.1 ISO out
device connected. With this filter driver, the PLL power down mode can be enabled to save additional power
when USB 1.1 ISO OUT devices are not connected. Customers who are enabling both L1 on AL-LINK and
the A-LINK PLL power down mode in the system BIOS will need to include the filter driver as part of their
operating system installation. The PLL power down mode can be enabled or disabled in SB700 BIOS CIMX
code. Systems that do not have the filter driver installed should disable the A-Link PLL power down mode
feature in the system BIOS.
Fix Planned
This issue is resolved in SB710/SB750 revision A14.