[Ardour-Users] smp questions etc

Sampo Savolainen v2 at iki.fi
Mon Aug 20 22:41:03 PDT 2007

Quoting Matthew Polashek <matt at tinysongs.com>:

> Ok, I'm throwing together a new box in which I will install  
> UbuntuStudio with the intention of using it as a live processing rig  
> for live performance using PD.  I'm interested in discovering whether  
> it makes more sense to get a Core 2 Quad processor that runs with a  
> bus speed of 1066 or a Core 2 Duo processor that runs with a bus  
> speed of 1333.  The idea is to reduce latency as much as possible.   
> I'll get I/O via a RME 9652 and a couple Behringer ADA8000 units.   
> Also, any thoughts on how ram speed plays into this equation?  I'm  
> looking at the Intel dg33fb board.

Ardour is multi-threaded, but at the moment, Ardours' audio processing is
run in a single thread. This means that the audio work done by jack cannot
be spanned over two processors. 

Using jackdmp will enable your system to run some jack clients in parallel
(depending on the connection scheme between them). But this only means that
different jack clients will be able to run in parallel. It doesn't make
Ardour process in multiple threads. 

This is something we will work on in the future, but at the moment, this
makes the choice quite clear: core 2 duo should suffice well. A quad core
will be more future proof though. I can't really comment on bus speed or ram
speed. Like always, the faster the better, but the question is how much of a
difference it will make? My guess is that while it would be faster, it
probably is not that much faster that you could run with half the buffer
size than with the slower bus/ram.

Before you get really dissappointed by this fact, remember that while only
one cpu can be used for ardour work, it means thath the second core (or rest
of them in the case of the quad) is free to run all those other tasks in
your system. This means that the ardour gui, the desktop and other
applications will be practically unaffected by the DSP load on your box.
This is a big boon on 2 cpu systems.


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