# Macbook Pro vs iMac TurboBoost with Logic?



## khollister (Mar 8, 2018)

So I just ran into a problem I'm guessing several of you have dealt with, and I'm hoping for some guidance.

I decided to set up my 2017 15" MBP w LPX as a travel rig. Main rig is 10 core 3.0GHz iMac Pro, laptop is 3.1GHz Kabylake. Both machines are similar architecture (except for more cache in the Xeon) and similar base clocks and turbo frequencies. The Geekbench single core benchmarks are also in the ballpark (5200 iMP vs 4600 MBP as I recall).

However there is a HUGE difference in the indicated realtime CPU load within Logic that is largely independent of what audio interface I use (I have tried both with the internal as well as my RME UCX - the UCX is better but not nearly enough to close the gap). I used Intel Power Gadget to look at what the CPU speed is doing on both and got a big surprise.

While the iMac Pro attempts to maximize CPU speed, staying around 4.0 - 4.2 GHz for lighter loads (like playing a single track), the MBP won't go above its base clock (3.0) unless I grab a handful of voices in a very CPU intensive Omni multi. Even then it only goes to 3.3 at best. The large disparity in clock speed appears to be the primary contributing factor in the LPX CPU differences. The MBP is on wall power BTW.

Curious what other MBP users see and has anyone else noticed big differences in performance between similarly spec'd MBP i7's and iMac's or Mac Pro's?


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## Symfoniq (Mar 8, 2018)

In Apple's relentless pursuit of thinness, they've built MacBook Pros that throttle under heavy CPU load. I've observed throttling behavior with the last three generations of MacBook Pro (all of which I've owned), with the current Touch Bar models being the worst offenders. It's a beautiful machine, but not a true workhorse, IMO.


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## khollister (Mar 8, 2018)

Symfoniq said:


> In Apple's relentless pursuit of thinness, they've built MacBook Pros that throttle under heavy CPU load. I've observed throttling behavior with the last three generations of MacBook Pro (all of which I've owned), with the current Touch Bar models being the worst offenders. It's a beautiful machine, but not a true workhorse, IMO.



I’m way below thermal throttling - CPU is only 60C. I’m certain the cause is power management for battery life. My question is whether I have something unique going on here and if not, has anyone run across a solution?


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## Symfoniq (Mar 8, 2018)

khollister said:


> I’m way below thermal throttling - CPU is only 60C. I’m certain the cause is power management for battery life. My question is whether I have something unique going on here and if not, has anyone run across a solution?



Okay, if it's not throttling, then how is it not behaving as expected? You state it's hitting 3.3 GHz—presumably on multiple cores—which is above the 3.1 GHz base clock. You're never going to see the 4.1 GHz max Turbo Boost except in a lightly threaded workload (for a single core to hit 4.1 GHz, the other three physical cores would have to be idle, or nearly so). Moreover, Turbo Boost limitations aren't just thermal, but also related to the total power available to the CPU. If the CPU is hitting 4.1 GHz or thereabouts in single-threaded benchmarks (Geekbench or Cinebench), then I'm inclined to say nothing is wrong.


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## khollister (Mar 8, 2018)

With nothing but Logic and a single voice on a single track, the iMP is clocking at close to the max single core turbo - 4.2 vs 4.5 - reasonable since there are very low levels of activity on other cores & consistent with published observations.

With the exact same stuff running and the same logic project, I'm seeing 3.0 (base clock) on the MBP. I only get to 3.3 with playing a couple handfuls of voices and pegging the Logic CPU meter. I would expect at least 3.5 in the single voice scenario.

I can reasonable assume that the turbo algorithm is less aggressive due to either microcode in the mobile CPU part or manipulation on the part of Apple to optimize battery life. There used to be a command line option with pmset in Terminal to control the CPU speed management but it was removed a few versions of Mac OS ago.

I'm not trying to start an argument about expectations here, I'm just trying to verify of A) this is similar to what other MBP users have experienced and B) is there a way to alter this that I don't know about?


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## Symfoniq (Mar 8, 2018)

khollister said:


> I'm not trying to start an argument about expectations here, I'm just trying to verify of A) this is similar to what other MBP users have experienced and B) is there a way to alter this that I don't know about?



No worries, khollister. I didn't think you were, and I'm not trying to, either. Sometimes tone is hard to convey in this medium.

My understanding is that in any given situation, Turbo Boost is either thermally limited, or power-limited (there's only so much voltage to go around to all the cores, particularly on lower-TDP CPUs). Beyond that, as you pointed out, there's a lot of other variables to consider, such as whether Apple is more conservative with the power management on the MacBook Pro than the iMac Pro.

You mentioned Geekbench. What max CPU frequency are you seeing when running Geekbench in single-threaded mode? I'll run the same test on my 2.9 GHz base clock 2017 15" MBP and we can compare notes.


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## Symfoniq (Mar 8, 2018)

FWIW, here are Geekbench/Cinebench/Intel Gadget results for a 2017 15" MacBook Pro with 2.9 GHz (3.9 GHz Turbo Boost) i7-7820HQ CPU. Despite the "3.9 GHz Turbo Boost", I never saw the CPU frequency exceed 3.63 GHz, even with Cinebench locked to a single thread (there no longer appears to be a way to do this in Geekbench).


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## khollister (Mar 8, 2018)

Symfoniq said:


> FWIW, here are Geekbench/Cinebench/Intel Gadget results for a 2017 15" MacBook Pro with 2.9 GHz (3.9 GHz Turbo Boost) i7-7820HQ CPU. Despite the "3.9 GHz Turbo Boost", I never saw the CPU frequency exceed 3.63 GHz, even with Cinebench locked to a single thread (there no longer appears to be a way to do this in Geekbench).



Haven't run GB yet, but I was guessing 3.5 - 3.6 as a max without actually locking the other cores, so that looks about right. I'll run mine in a few.


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## khollister (Mar 8, 2018)

OK - good news is the single thread score was 4833, a bit higher than the average listed on the GB site for this model. The bad news is my Power Gadget graph looked similar to yours with a few periodic spikes to about 3.5-3.6 but well below the base clock most of the time. I'll download cinebench and see what happens

UPDATE: OK - Cinebench CPU single thread has me hovering between 3.6-3.78


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## khollister (Mar 8, 2018)

ran GB on the iMac Pro. While the single thread score was a bit low (5083 instead of 5200 - I wasn't anal about shutting everything off first), the CPU speed was constant between 4.0 and 4.2 for the first half and then bounced between 3.6 and 4.0 for the 2nd part where it was loading all the cores more. The power was spiking up to the max TDP of 140W during that.

Clearly either Intel or Apple (or both) have programmed a very different power management profile on the laptops vs the desktop Xeon stuff. I certainly understand what I'm seeing in Logic now, but I still wonder if there is some way influence the down clocking of the mobile CPU.

And while the closeness of the single thread GB scores between the 2 machines (4800 vs 5080) would lead you to expect similar performance on record armed tracks in LPX (which are single threaded by design), the reality is very, very different. Moral of the story is the single threaded part of the GB test is fairly useless on predicting real time DAW performance on record armed tracks.


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## Symfoniq (Mar 8, 2018)

khollister said:


> ran GB on the iMac Pro. While the single thread score was a bit low (5083 instead of 5200 - I wasn't anal about shutting everything off first), the CPU speed was constant between 4.0 and 4.2 for the first half and then bounced between 3.6 and 4.0 for the 2nd part where it was loading all the cores more. The power was spiking up to the max TDP of 140W during that.
> 
> Clearly either Intel or Apple (or both) have programmed a very different power management profile on the laptops vs the desktop Xeon stuff. I certainly understand what I'm seeing in Logic now, but I still wonder if there is some way influence the down clocking of the mobile CPU.
> 
> And while the closeness of the single thread GB scores between the 2 machines (4800 vs 5080) would lead you to expect similar performance on record armed tracks in LPX (which are single threaded by design), the reality is very, very different. Moral of the story is the single threaded part of the GB test is fairly useless on predicting real time DAW performance on record armed tracks.



Interesting results.

Intel notes on the spec sheet for these CPUs that the system integrator can customize the TDP down another 10 watts, which would definitely have an impact on Turbo Boost performance since voltage to the CPU would have to be reduced sooner. Can't say for sure if that's the case here, but clearly something other than heat is preventing our CPUs from hitting the max Turbo Boost number. A quick Google search reveals there are other complaints about MacBook Pros never hitting max Turbo Boost, too.


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