smp questions etc

[Jonathan Leonard]

On Aug 20, 2007, at 7:04 PM, Matthew Polashek wrote:

> 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.

Hi Matt, have you checked out www.dawbench.com?  While that site does  
not specifically deal with linux, it has a lot of information and  
test results comparing daw performance over a range of processor  
counts and buffer sizes.  There is some contention about the utility  
of multiple processors or core for low latency needs because of the  
overhead in syncing and managing more than 1 cpu.  Some developers  
claim that with smp 10 ms is the effective lower limit because below  
this you waste cpu.  Its a shame because most new hotrod machines are  
multicore.  IIRC from that site, there seems to be some benefit in  
having dual core, but less and less as you go up - for low latency  
use where you really have to work at 8ms or less.  As a rule it is  
not my impression that adding any more cpu or core will help latency,  
but perhaps make it worse.  But I too am learning about this in linux  
and maybe things are entirely different.

If anyone has additional information to share regarding low latency  
SMP in linux and the application of 'computer as musical instrument',  
I would also really appreciate this!

Thanks,

Jonathan Leonard