User Manual

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User's Guide Digiface AVB © RME
The Digiface AVB also supports USB 2, where the number of record and playback channels are
halfed due to the limited bandwidth (up to 48 kHz: 64 channels, up to 96 kHz: 32 channels, up
to 192 kHz: 16 channels). The number of channels accessible via TotalMix FX, the network ins
and outs, stays identical to USB 3 operation. Good performance and click-free operation even
at low buffer sizes are indeed possible on current computers. However, using older computers a
simple stereo playback might cause a CPU load of more than 30%.
Best USB 2 performance is achieved by connecting the Digiface AVB to its own bus, which
should be no big problem as most USB 2.0 interfaces are a double bus design. A check in the
Device Manager can be done as follows:
Connect the Digiface AVB to a USB 2 port
¾ Start the Device Manager, View set to Devices by Connection
¾ Select ACPI x86-based PC, Microsoft ACPI-Compliant System, expand PCI Bus
This branch normally includes two entries of a USB2 Enhanced Host Controller. A USB Root
Hub can be seen, which then connects all USB devices, including the Digiface AVB. By recon-
necting to a different port this view shows at which of the two controllers the Digiface AVB is
connected. With multiple devices it can be checked if they are connected to the same controller.
Furthermore this information can be used to operate an external USB drive without disturbing
the Digiface AVB, by simply connecting the drive to the other controller.
It can also be used to check where and in what combination USB 3 is used. In fact many mod-
ern motherboards have an additional chip to the mostly found Intel chipset, adding further USB
3 ports. But documentation is often unclear about which port/socket is connected to which chip.
By connecting the Digiface AVB and using the procedure above one can easily see the current
connection, ensuring the Digiface AVB is really connected to the Intel chipset and not to some
other flaky one.
Especially with notebooks it can happen that all internal devices and all the sockets/ports are
connected to the same controller, with the second controller not used at all. In that case all de-
vices have to use the same bus and will interfere with each other.
A computer blocked for a short time – no matter if ASIO or WDM – will lose one or more data
packets. Such problems can only be solved by increasing the buffer size (latency).