[LAU] Does the link of 2 units decrease the DSP load? (and more questions about DSP under GNU/Linux)
tyranorl at free.fr
Fri Sep 10 16:57:20 UTC 2010
My question is in the subject: Do the use of 2 units linked decrease the
I'm currently using a Focusrite Saffire Pro 40 with FFADO 2.1 and
jackdmp on a Core2Quad Q6600 processed machine with 8 Gb RAM.
The setup I use loads the DSP at 65%.
If I add a new Focusrite Saffire Pro 40, chained to the first one, will
the DSP load decrease?
*Discussion you may not want to read*
I'm at a point where I must increase the performance of my machine, as I
will pass from 8 analog ins and 10 analog outs to 24 ins and 8 outs.
I've tried my current setup (same softs, same machine) with a RME HDSP
9652, and came to a DSP load of 35%.
I now have two options:
1. buy a RME HDSP 9652, use my Focusrite Saffire Pro 40 as a 8-Pres unit
coming through ADAT to the RME, and buy 2 more Octopre or Saffire Pro
+ : DSP load is lower
+ : RME clock is better than the Focusrite one
+ : use of a PCI device => no use of FireWire, less cables, use of
stable drivers (already packaged in Debian)
- : more expensive (about 1250 €)
- : this setup is limited to 24 analog ins, and cannot be raised
2. buy another Saffire Pro 40, linked to the first one, and then buying
only one OctoPre.
+ : cheaper (about 850 €)
+ : this setup can be easily upgraded to a 32 analog ins
+ : more outs and more S/PDIF ins
+/- ? : DSP load decreased with link of the unit?
- : DSP load for one unit is higher
 One of my jobs is to make live sounds, and with such a system, I'm
able to replace a analog mixer for FOH, coming to a solution looking
like LS-9 (with better pres) and other digital mixers.
Last but not least, last time I wondered about the use of DSP in
GNU/Linux, I finally understood that the DSP of audio interfaces weren't
use under GNU/Linux.
Am I wrong?
Is it always true?
If yes, how does it come that for a very same PC/software setup the RME
(PCI, so alsa driver) DSP load is twice lower than the Focusrite
(FireWire so FFADO) one?
Thanks a lot.
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