Logic Pro 9 iMac Quad Core Hyper-Threading & Logic 9

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DeeJay SchmeeJay

Logician
The new Quad Core iMac comes with an i5 processor which doesn't do hyper-threading, or an i7 processor which does...

From a non-technical perspective I understand basically what hyper-threading does (enables the OS & program to see 8 virtual cores instead of 4 real cores).

But in real-world usage of Logic 9, would it make a significant difference?
 
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I don't think so, at least not yet. It's my understanding that real-time applications have problems using "virtual" cores, performance is not improved and in some cases not as good.

Common practice on Windows machines was to disable HT in the BIOS.
This can be done on the Mac via the terminal, at least that's what I've read.

I think it was Logic 9.0 that displayed 16 (8 + 8 virtual) cores on a Mac pro i7 machine, the virtual cores were never used no matter how complex the project. By the time either version 9.01 or .02 rolled around Logic no longer displayed 8 + 8 but was back to displaying only the 8 hardware cores.

I'd be interested if anyone had any new info.

Howard
 
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Thanks Howard - gives me food for thought.

Makes me wonder whether the i5 (dues to it's lack of hyperthreading) would actually be less prone to niggles and crashes - not to mention running cooler.
 
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On my old dual G5 Powermac, Logic 9 only uses one core when bouncing offline. Is this also the case with the new Intel multi-cores?

Ben
 
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benst said:
On my old dual G5 Powermac, Logic 9 only uses one core when bouncing offline. Is this also the case with the new Intel multi-cores?

Ben
Click to expand...

Yes, that is a different issue, nothing to do with how many cores a Mac has, offline bounce on one core is a logic limitation.

kind regards

Mark
 
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Ok, thanks, Mark.

I was hoping it was a limitation/bug of the PowerPC binary. This kinda sucks because if you have a lot of plugins it is actually faster to bounce online (using all cores) than offline.

Ben
 
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Markdvc said:
Yes, that is a different issue, nothing to do with how many cores a Mac has, offline bounce on one core is a logic limitation.
Click to expand...

Mark, I'm just curious as to why Bounces are restricted to the one core...
Is this just a left over from the older versions of Logic, or does it have something to do with the OS? Or neither?
Seems like faster bounces would be a nice selling point for Logic 9.

Do other DAW's take advantage of multi-core processors for bounces?:huh:

Thanks!
 
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My understanding is that an offline bounce is handled as a single thread, which can only run on one core. I'm not a programmer so have neither details as to why this is, nor do I know whether it is impossible, or "merely" very complicated to change. I think that it is safe to assume that if it was an easy fix, it would have been fixed, it has been discussed intensely in various fora since at least the early days of Logic 8.

Real time bounces are not effected by this, as can be seen by leaving Logic's CPU meter visible when bouncing, and by the fact that often, any medium size arrangement may take longer to bounce offline than online. Of course, that gets to be a major PITA when dealing with arrangements which are both long and large.

kind regards

Mark
 
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As I understand it, a single audio channel strip (whether stereo or mono) including inserts & channel eq runs as a single thread, this goes for virtual instrument channel strips as well.

The Master Fader is a special purpose channel strip and the same rules apply and as Mark mentioned, a single thread can use only one core.

Whether or not this could change is anyone's guess. Snow Leopard has the "central station" feature which is supposed to make better use of the Intel multi-core processors but the application would have to support that function.

Howard
 
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This thread veered off into a discussion of core usage and bouncing, but I want to bring it back to this question: Is it worth spending the extra $200 for an i7 processor?

Jim
 
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pfloyd714714 said:
...I want to bring it back to this question: Is it worth spending the extra $200 for an i7 processor?
Click to expand...

I've had a look at some of the bench-test results and the i7 is definitely a faster processor. But none of these tests really relate to real-world use of audio apps like Logic. I think the only way to tell is to set the same session up on two machines to compare.

I'll be receiving an iMac i5 with 8Gig RAM sometime in the next month (orders are arriving slowly in Australia) and I'd be happy to compare results with an i7 owner. I remember someone had set up a "structure VI test" session in the past. I wonder if that still exists?
 
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