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Level 1

2 points

New Mac Pro - 6 or 12 cores for Logic?

Hi

I'm about to place an order for a new Mac Pro, to replace our previous Mac Pro.

Does anyone know if the 12 or the 6 core model is likely to deliver the best performance with Logic? The 6 core is clocked higher than the 12 core - 3.33GHz v 2.93GHz - and it's hard to get a handle on whether the additional cores are likely to compensate for the lower speed.

Does anyone who knows more than me about this stuff have a view? Is Logic even able to fully utilize all 12 cores?

On our current 8-core system I tend to see activity across 4 or 5 cores only, and the times we hit performance issues are when 1 particular core is being maxed out, even though others are idle or running at low load. That said, we're still using OS 10.5 so maybe load balancing is improved with 10.6.

Any help or advice very much appreciated.

Jules
http://www.trailermen.com

Mac Pro 8 Core, Mac OS X (10.4.10)

Posted on Aug 12, 2010 6:40 AM

Best reply

Mike Connelly

Level 4

1,791 points

Posted on Aug 12, 2010 7:32 AM

Nobody knows yet. I'd wait until they are shipping, which should only be a week or two, and see what the user reports online are from Logic users.

Also, as you have seen, Logic is not well optimized for all numbers of cores. When the new hardware is released, it's possible that Logic will be updated at some point to better utilize more cores, or it may take months or years to catch up with the hardware (the current situation). If you have an eight core already, personally I'd stick with that since it's not being used to its full potential yet. Is it a 2008 or 2009 MP?

You may be able to adjust your sessions to better balance the load, check this out:

http://support.apple.com/kb/HT3161

View in context

201 replies

Aug 13, 2010 10:31 AM in response to Eriksimon

Another possibility is that the 12 core machine will use the main cores but not the HT cores (for whatever reason), in which case the rep was telling the truth but half the hardware will still be sitting there which would be a big disappointment. Personally, I'd follow up with an apple rep and ask about HT cores.

Aug 14, 2010 5:22 AM in response to Mike Connelly

A 12 core machine has only 12 cores ! There are not more cores. With HT it will show you 24 Cores, but the HT-cores will use only the 12 hardware-cores. HT-cores share the same cores, they are virtual.
Or do i miss something ?

Cheers

spheric

Level 3

699 points

Aug 14, 2010 5:31 AM in response to Heiko_Britz

The point is that hyperthreading increases performance by better distributing load among the physical cores.

I've seen conflicting reports on whether that actually applies to audio processing, but that's the basic point.

Eriksimon

Level 6

15,422 points

Aug 14, 2010 5:44 AM in response to Heiko_Britz

Yes. Logics' performance will "virtually" double with 12 extra "virtual" cores.
Logic on a quad core plus HT is only about 10% less powerful than Logic on a Mac Pro with 8 real cores. So 12 virtual cores could be expected to raise Logics' ceiling somewhere between 75-90 %. Pretty significant.

Aug 14, 2010 12:48 PM in response to Heiko_Britz

Heiko_Britz wrote:
A 12 core machine has only 12 cores ! There are not more cores. With HT it will show you 24 Cores, but the HT-cores will use only the 12 hardware-cores. HT-cores share the same cores, they are virtual.
Or do i miss something ?

You're thinking of the old implementation of HT from years ago where the HT cores were virtual (and were mostly worthless in many cases).

The newer implementation is actual hardware cores, not virtual ones. The HT cores are only partial cores and share a section with the main core, but they are actual physical extra hardware and do provide extra performance in many cases (including Logic in the case of quad i7 or xeon configs). So the 12 core machines are actually 12 full cores plus 12 partial cores for a total of 24 cores.

Aug 23, 2010 8:20 AM in response to Trailerman

First 6 core results are online, looks like that apple rep didn't know what they were talking about. See other thread. Did you end up ordering a machine?

Trailerman Author

Level 1

2 points

Aug 23, 2010 10:36 AM in response to Mike Connelly

Hi Mike

Doesn't look too good from that benchmark. Unfortunately he didn't run any comparisons with his other machines, so it's a little hard to draw precise conclusions not knowing how his machine is set up, but I agree it looks pretty underwhelming.

The problem is we have no real basis for comparison. For example, if we ran that test on a 12 core machine, would it use 6 of the cores, or only 3 or 4? All seems kind of weird to me.

I think you're implying that Logic is basically broken when running on the new Macs, which it may well be, but I doubt Apple will leave things in that state for too long, if it is the case.

I have a 12 core 2.93 GHz on order, and am constantly trying to get more information on performance, as I can change or cancel my order at any time, so please keep the info coming ...

Thanks and regards

Jules

Aug 23, 2010 10:49 AM in response to Trailerman

The basis for comparison is running that same benchmark on other machines, and quads get 50 tracks or more, even with a much lower clock speed. Logic absolutely is broken on the 6 core machine if it is performing worse than a quad. The 12 core may or may not fare better although this doesn't make me too optimistic.

If this doesn't get apple to optimize the app, nothing will. It's one thing to have cores sitting there unused, it's another for more cores to make performance get worse.

Pancenter

Level 6

14,644 points

Aug 23, 2010 11:10 AM in response to Trailerman

Trailerman wrote:
I think you're implying that Logic is basically broken when running on the new Macs, which it may well be, but I doubt Apple will leave things in that state for too long, if it is the case.

Jules, if you've been following these threads you must realize it's been like that for quite some time now.

pancenter-

Aug 23, 2010 11:13 AM in response to Pancenter

Logic has left cores sitting there unused for some time now (more cores not really increasing performance). As far as I know, having more cores actually degrade performance is new to the six core.

Trailerman Author

Level 1

2 points

Aug 24, 2010 1:30 AM in response to Mike Connelly

Mike - would the benchmark in question normally max out all available cores?

It's not a test I'm afamiliar with, so I don't know to what extent it allows Logic to use all the CPU's on the system.

Obviously if on other systems it maxes out all the cores, then there is a fundamental issue with Logic when running on the new generation of Mac Pros. The track count, when Logic is fixed, should be around double that reported. ie. the issue currently is a software one which Apple must surely address and fairly urgently.

If the benchmark behaves similarly on other systems, in that it only uses half the available cores, then the situation is more worrying. It suggests that the new machines are actually slower than previous generations. Hard to believe, but perhaps there's a quirk of Logic's coding which means the current architecture is does not suit it. I'd be very surprised if this was the case.

I think the likely scenario is that there is a software issue with Logic, and this is the reason Apple posted no performance Logic benchmarks for the new Mac Pros. All us users can do is hassle our reps and try and find out what's going on and what's being doen about it.

I'd still like to see some bechmarks for the 12 core machine, because it might shed a little more light on where the problem lies.

Jules

Aug 24, 2010 7:55 AM in response to Trailerman

Trailerman wrote:
I think the likely scenario is that there is a software issue with Logic, and this is the reason Apple posted no performance Logic benchmarks for the new Mac Pros.

Looks like the most likely possibility (especially since the same results are seen when you turn off two of the cores on an octo to simulate a six core machine, which I posted a few weeks back).

I don't think Logic generally maxes out any cores, but at least on the quad machine it uses the four cores plus the four HT cores. It looks like these machines are much faster than the previous generation (as seen on every other benchmark that has been run on them) but Logic just isn't programmed to run properly on six cores. They should have been aware that six core machines were likely in the future but for whatever reason they didn't cover that possibility. And the results from a 12 core machine should be interesting, I doubt all cores will be used but it may not even perform better than an eight core.

Aug 24, 2010 11:03 AM in response to Mike Connelly

Mike Connelly wrote:

You're thinking of the old implementation of HT from years ago where the HT cores were virtual (and were mostly worthless in many cases).
The newer implementation is actual hardware cores, not virtual ones. The HT cores are only partial cores and share a section with the main core, but they are actual physical extra hardware and do provide extra performance in many cases (including Logic in the case of quad i7 or xeon configs). So the 12 core machines are actually 12 full cores plus 12 partial cores for a total of 24 cores.

Do you have any info to clarify this? Wiki says still "virtual". They are not half-cores or anything. It is a virtual representation of allowing 2 threads per physical core. And is fully dependent on the OS. This appears to be true for all current implementations. Logical cores are not physical cores.

http://en.wikipedia.org/wiki/Hyper-threading

maceasy

Level 1

24 points

Aug 24, 2010 11:29 AM in response to Trailerman

Guys, you are disappointed that Logic doesn't use all cores. But Logic is only like many other apps in this respect. Take a look at Barefeats benchmarks:

http://www.barefeats.com/wst10.html

These benchmarks are useful, but note the caveats at the bottom: the tests use all cores - most apps don't:

"Although the 12-core Mac Pros score best, these benchmark apps use all cores to full advantage. In the real world, only certain apps are capable of using all cores. More often than not, these apps use them inefficiently or run faster if you limit the number of active cores. I'm speaking of apps like After Effects CS5 and Compressor 3.5.

There are other MP aware apps like Photoshop, iMovie, and Aperture which only use a portion of the cores no matter how many real or virtual cores there may be. There are yet others (such as Motion and iTunes) that only use one core, though Motion uses the GPU as a co-processor.

In defense of 12-core Mac Pros, as applications are improved to utilize their full potential, they will justify their existence more strongly."

So Logic is not at all exceptional. The really interesting thing I find from these scores is that the now discontinued Nehalem 8 core is the next best after the 12 cores.

Aug 24, 2010 11:35 AM in response to maceasy

The apps he tested with are "best case" scenarios as they are optimized for benching the raw power of a CPU. That is all. Geekbench and Cinebench scale quite well and are made for multicore.

New Mac Pro - 6 or 12 cores for Logic?