[FFADO-devel] wiki, FAQ: How many devices can I use at the same time?

[Stefan R. <st...@s5...>]

Hi,

it appears that I cannot edit your FAQ. :-)  ("Method Not Implemented
POST to /wiki/FrequentlyAnsweredQuestions not supported.")

Here is a suggestion for the section "How many devices can I use at the
same time?":

[...]
You are not likely going to be able to use more than 4 devices on the
same host controller. This due to the fact that most host controllers
have only 4 "isochronous DMA contexts" in each direction (send/receive).
Every isochronous stream needs one. (Additional DMA contexts exist for
asynchronous traffic, i.e. device discovery and control; these contexts
do not impose a limit on the number of usable devices.) One Saffire
requires an isochronous stream in each direction, hence using one
context per direction.

[...]
It e.g. means that the Texas Instruments controller can accommodate 4
receive and 8 transmit contexts, meaning up to 4 audio devices (at least
theoretically).

If there is an active IP-over-1394 networking interface, i.e. either the
eth1394 or firewire-net kernel driver is loaded and its interface was
opened with ifup or otherwise, then one of the isochronous receive DMA
contexts is taken away for IP broadcast and multicast traffic.
[...]

-- 
Stefan Richter
-=====-==-=- --=- ===--
http://arcgraph.de/sr/