2018 MBP 13"- Slow with an external monitor

Rigtee

macrumors member
Original poster
Sep 19, 2018
33
16
Belgium
Hello everyone,

I've owned a 2018 MBP 13" (quad-core CPU-i5 2.3GHz, 16GB RAM) for about a year and recently I bought a 32" 4K external monitor (BenQ EW3270U) to work more comfortably with it while at home.

With the Thunderbolt 3 USB-C port, I was expecting the machine to be pretty fast (the cable from the screen is directly plugged into the laptop) and although it is the case for *very* simple tasks (web browsing, listening to music, typing documents), it is definitely slowing down when I'm asking for more. Lightroom editing for instance is really a pain in the arse: somewhat smooth when used on the Mac directly but sluggish when connected in clamshell mode to the screen. Same story when viewing a video on YT, the fullscreen on/off animations are not smooth. I'm using the scaled resolution of 2560x1440 (in 1080p, true "retina" mode, the text was too big for my liking and in native resolution it is illegible).

Of course I'm being picky here. It does perform well most of the time. But isn't it legitimate to complain about the lack of smoothness when I'm doing "pro" work? Isn't such a modern €2500 machine supposed to handle everything you throw at it perfectly?

Might a dedicated GPU be useful for that kind of scenario?

Thanks!
 
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cynics

macrumors G4
Jan 8, 2012
11,313
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I have the same Mac as you except 8gb RAM.

Your GPU is lacking for that workload. The UI uses hardware acceleration so its really fast and fluid. If the GPU is being heavily used by another program you'll get UI stutter and lag. You can see this for yourself if you stop most foreground processes, open activity monitor and goto the menu bar, Window > GPU History and then start swiping the UI around. You'll see the spikes in the graph fr.

Keep in mind that your monitor is capable of requiring a lot of system resources at the drop of a hat. For comparison a 1080p 60hz 8bit monitor requires bandwidth of 4-5Gbps.. That BenQ monitor is 4k 60hz 10bit which can exceed 20Gbps. And that is just the bandwidth requirements, that data still needs to be processed.

Using a scaled resolution isn't helping with performance either.

Plus you have 1.5gb of VRAM for a piece of software (Lightroom) that has a minimum requirement of 2gb of VRAM when used with a 4-5k monitor but they recommend 4gb of VRAM. Personally I always consider the recommended spec as being the minimum spec and I'll try to exceed it a bit. You are below the minimum....

I don't feel the lack of UI smoothness is a legitimate complaint under these specific conditions. Regardless of any computers specs or how "Pro" it is you can find a way to bottleneck performance.

To illustrate my point above this is just playing a 4k60hz HDR video from YouTube (FireFox browser) on an external 4k60hz HDR display from my MacBook via USB cable (no hub).

Screen Shot 2019-09-07 at 11.04.43 PM.png


CPU usage is so high because the video was encoded with VP9 (if it was HEVC I doubt it would have played very smooth). Since the video was buffering the CPU usage and temps were dropping off toward the end. Prior to that CPU temps were around 90c with the fans at max. And it was throttling on power consumption limits. Just to play a video....Maintained a nice all core turbo the entire time though....
 
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Rigtee

macrumors member
Original poster
Sep 19, 2018
33
16
Belgium
I have the same Mac as you except 8gb RAM.

Your GPU is lacking for that workload. The UI uses hardware acceleration so its really fast and fluid. If the GPU is being heavily used by another program you'll get UI stutter and lag. You can see this for yourself if you stop most foreground processes, open activity monitor and goto the menu bar, Window > GPU History and then start swiping the UI around. You'll see the spikes in the graph fr.

Keep in mind that your monitor is capable of requiring a lot of system resources at the drop of a hat. For comparison a 1080p 60hz 8bit monitor requires bandwidth of 4-5Gbps.. That BenQ monitor is 4k 60hz 10bit which can exceed 20Gbps. And that is just the bandwidth requirements, that data still needs to be processed.

Using a scaled resolution isn't helping with performance either.

Plus you have 1.5gb of VRAM for a piece of software (Lightroom) that has a minimum requirement of 2gb of VRAM when used with a 4-5k monitor but they recommend 4gb of VRAM. Personally I always consider the recommended spec as being the minimum spec and I'll try to exceed it a bit. You are below the minimum....

I don't feel the lack of UI smoothness is a legitimate complaint under these specific conditions. Regardless of any computers specs or how "Pro" it is you can find a way to bottleneck performance.

To illustrate my point above this is just playing a 4k60hz HDR video from YouTube (FireFox browser) on an external 4k60hz HDR display from my MacBook via USB cable (no hub).

View attachment 856608

CPU usage is so high because the video was encoded with VP9 (if it was HEVC I doubt it would have played very smooth). Since the video was buffering the CPU usage and temps were dropping off toward the end. Prior to that CPU temps were around 90c with the fans at max. And it was throttling on power consumption limits. Just to play a video....Maintained a nice all core turbo the entire time though....
Thanks a lot for your thorough and in-depth answer!

I did not think the GPU might bottleneck the performance here but it seems logical after all, having integrated graphics while driving a 4K monitor and doing some Lightroom work (which is not known as the most-optimised piece of software on MacOS) does not maximising the chances to perform well.

Anyway, I might then accept the reality as it is and move on. Actually I sold one year ago my 2016 15" MBP for keyboard reliability issues and now kinda regret it when I'm doing some video/photo editing. Buying an eGPU is not the best option for me as it is expensive and not that minimalist. I might then look for a 2019 15" MBP if such a problem repeats itself in the future...or simply wait for the 16" MBP everyone is talking about ;)
 

cynics

macrumors G4
Jan 8, 2012
11,313
1,696
Thanks a lot for your thorough and in-depth answer!

I did not think the GPU might bottleneck the performance here but it seems logical after all, having integrated graphics while driving a 4K monitor and doing some Lightroom work (which is not known as the most-optimised piece of software on MacOS) does not maximising the chances to perform well.

Anyway, I might then accept the reality as it is and move on. Actually I sold one year ago my 2016 15" MBP for keyboard reliability issues and now kinda regret it when I'm doing some video/photo editing. Buying an eGPU is not the best option for me as it is expensive and not that minimalist. I might then look for a 2019 15" MBP if such a problem repeats itself in the future...or simply wait for the 16" MBP everyone is talking about ;)
I tend to agree, I'm not a huge fan of an eGPU because my workload doesn't warrant one. However if it did it could be an invaluable addition.

Something of note about a dedicated GPU (internal or external) is the biggest gain to performance when it comes to productivity (video editing, photo editing, etc) is just having dedicate graphics. The card itself doesn't matter as the initial gain is moving the load off the CPU to free it up for CPU task. The specific GPU used will show performance gains depending on the actually task and its requirements.

You really wouldn't need to break the bank for Lightroom.

An eGPU is upgradable down the road once you have the case so you keep a minimalist laptop and just plug into the eGPU.

An eGPU doesn't need to be front and center on your desk. I keep all my peripherals on a shelf I built under my desk so there is only one USB C cable that plugs into the laptop on the desk, under the desk it breaks out for the external display, ethernet, etc etc...

Just food for thought...
 
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Fishrrman

macrumors P6
Feb 20, 2009
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OP wrote:
"I'm using the scaled resolution of 2560x1440 (in 1080p, true "retina" mode, the text was too big for my liking and in native resolution it is illegible)."

THERE'S your problem.

It takes a lot more "computing horsepower" to run a 4k display in scaled mode than in native mode (either full 4k or HiDPI). This is slowing down the MacBook Pro.

You have three choices that I see:
1. Set the display for 4k HiDPI mode (looks like 1080p)
or
2. Get a 27" 4k display and run THAT in 4k HiDPI mode (looks like 1080p but the text will be smaller)
or
3. Get a 32" NON-4k display. That will run in native 1440p mode and will be easy for the MBP to handle.

The MBP will run much better with ANY of the above solutions.
 
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Rigtee

macrumors member
Original poster
Sep 19, 2018
33
16
Belgium
I tend to agree, I'm not a huge fan of an eGPU because my workload doesn't warrant one. However if it did it could be an invaluable addition.

Something of note about a dedicated GPU (internal or external) is the biggest gain to performance when it comes to productivity (video editing, photo editing, etc) is just having dedicate graphics. The card itself doesn't matter as the initial gain is moving the load off the CPU to free it up for CPU task. The specific GPU used will show performance gains depending on the actually task and its requirements.

You really wouldn't need to break the bank for Lightroom.

An eGPU is upgradable down the road once you have the case so you keep a minimalist laptop and just plug into the eGPU.

An eGPU doesn't need to be front and center on your desk. I keep all my peripherals on a shelf I built under my desk so there is only one USB C cable that plugs into the laptop on the desk, under the desk it breaks out for the external display, ethernet, etc etc...

Just food for thought...
True, but then comes the question: should I do “serious work” like Lightroom or Final Cut on the go? If yes, then I might switch back to a 15”.

I think I’ll hold to my 13” for the upcoming months and, instead of telling myself that I need that extra power, see if I encounter cases where I wish I had a dGPU. Then it’ll time to switch or to buy an eGPU.
[doublepost=1568727485][/doublepost]
OP wrote:
"I'm using the scaled resolution of 2560x1440 (in 1080p, true "retina" mode, the text was too big for my liking and in native resolution it is illegible)."

THERE'S your problem.

It takes a lot more "computing horsepower" to run a 4k display in scaled mode than in native mode (either full 4k or HiDPI). This is slowing down the MacBook Pro.

You have three choices that I see:
1. Set the display for 4k HiDPI mode (looks like 1080p)
or
2. Get a 27" 4k display and run THAT in 4k HiDPI mode (looks like 1080p but the text will be smaller)
or
3. Get a 32" NON-4k display. That will run in native 1440p mode and will be easy for the MBP to handle.

The MBP will run much better with ANY of the above solutions.
Is the scaled resolution affecting my performance that much? I’ll try to do the same task (editing photos in LR) using the HiDPI mode of 1080p, looks a bit big but I’ll get used to it. 4K native is not an option for me, have good eyes but uncomfortable.

I actually bought that screen of that size to play some games as well, that’s why it’s not the “ideal screen and resolution ratio” for a Mac.