Performance degrading on sustained workload w/ external monitor? MBP 16"

[swaggypee]

I'm getting performance issues on the new MBP 16" (i9 2.3 GHz, 5500M 4GB) when connecting to an external monitor. As I increase the workload (CPU only heavy tasks), the laptop gets slower and slower, to the point that it throttles to as low as 1.9 GHz. The thermals remain constant at around 75 - 80 degrees celsius, and the fans are at full blast. Meanwhile, when the external display isn't connected, I maintain about 2.8 Ghz, with the thermals being slightly warmer, but never above 90 degrees. I understand that there should be some performance degradation due to powering the monitor, but it can't be this bad right?

I uploaded two screenshots of intel power gadget which shows the beginning of the workload. The first one is connected to an external monitor, and the second one isn't.

Just wondering if this is normal, or if there's anything that can be done about it.

Thanks!

 

[matram]

I would recommend iStat menus to give you more information. I would guess that the GPU is also running hot because you use an external monitor.

 

[swaggypee]

Thanks for the recommendation! I download iStat and looked at the temperatures, and it seems like the GPU is staying fairly cool relative to the CPU temps, so that's probably not it

Uploaded a screenshot, while the computer was under load, and the temps are in F instead of C (not sure how to change it).

 

[M3Jedi77]

Which monitor are you using?

How can Apple say this MBP will drive 2 6K XDR displays if it struggles like this (according to a few forumers) powering just 1 4K!?

 

[swaggypee]

I'm using the Dell U3818DW (3,840 x 1,600 resolution).

Yeah, it's pretty upsetting, and I would assume that this would also happen on monitors with a lower resolution as well. After some time, intel power gadget shows that the laptop would refuse to use more than 35W of power, even though it can sustain ~55W without the external display.

 

[M3Jedi77]

I'm using the Dell U3818DW (3,840 x 1,600 resolution).

Yeah, it's pretty upsetting, and I would assume that this would also happen on monitors with a lower resolution as well. After some time, intel power gadget shows that the laptop would refuse to use more than 35W of power, even though it can sustain ~55W without the external display.

Wow. My MacBook Pro 16" comes this week and I was planning to power an XDR display, but this is worrisome. Can you run some more expirments and post more iStat screenshots? Would like to see the CPU & GPU panel specifically.


Your Dell is just 6.1 Million Pixels.

Two XDR displays would be 40.7 Million Pixels. Having a hard time believing the 16MBP can power that without killing itself.

 

[x3sphere]

Are you running in clamshell mode? Found it runs much cooler when connected to an external display with the lid closed.

I did not notice this on the i7 model with my 3440x1440 display, and I was running it at 120 Hz. Returned it for an i9 though. Will test when it arrives on Wed

 

[swaggypee]

Wow. My MacBook Pro 16" comes this week and I was planning to power an XDR display, but this is worrisome. Can you run some more expirments and post more iStat screenshots? Would like to see the CPU & GPU panel specifically.


Your Dell is just 6.1 Million Pixels.

Two XDR displays would be 40.7 Million Pixels. Having a hard time believing the 16MBP can power that without killing itself.

No problem, I'll post some pictures tomorrow when I start working on the laptop again.

Are you running in clamshell mode? Found it runs much cooler when connected to an external display with the lid closed.

I did not notice this on the i7 model with my 3440x1440 display, and I was running it at 120 Hz. Returned it for an i9 though. Will test when it arrives on Wed

Yeah I actually tried this when I was troubleshooting, and interestingly I had the same performance in clamshell and with the lid open.

 

[nethead]

I can reproduce this on my MBP (i9 2.4 GHz, 5500M 8GB), although not to that extent.

It seems like the GPU and the CPU compete for a shared power or thermal budget. When an external display is connected directly to the MBP, the Radeon constantly pulls 20W. If not, it pulls 5W. The 15W difference is exactly the amount that the CPU uses less under constant load. Not using an external display or connecting the display via an eGPU results in ~10 - 15% better CPU performance as measured in Cinebench R20.

The tests were run with only Cinebench R20 running, configured to a minimum test duration of 10 minutes. The score in the table was the one after the last run.

Here's my data:

It seems that neither clamshell mode nor the choice power adapter matter much for constant-load performance. I have the feeling that it's a power budget more than a thermal budget, looking at the CPU temperature.

Edit: Reran the dGPU measurements and added CPU temperatures.

 

[alfogator]

I can reproduce this on my MBP (i9 2.4 GHz, 5500M 8GB), although not to that extent.

It seems like the GPU and the CPU compete for a shared power or thermal budget. When an external display is connected directly to the MBP, the Radeon constantly pulls 20W. If not, it pulls 5W. The 15W difference is exactly the amount that the CPU uses less under constant load. Not using an external display or connecting the display via an eGPU results in ~10 - 15% better CPU performance as measured in Cinebench R20.

The tests were run with only Cinebench R20 running, configured to a minimum test duration of 10 minutes. The score in the table was the one after the last run.

Here's my data:
View attachment 883052

It seems that neither clamshell mode nor the choice power adapter matter much for constant-load performance. I have the feeling that it's a power budget more than a thermal budget, looking at the CPU temperature.

Edit: Reran the dGPU measurements and added CPU temperatures.

I have a feeling you don't use dark mode ?

 

[swaggypee]

I can reproduce this on my MBP (i9 2.4 GHz, 5500M 8GB), although not to that extent.

It seems like the GPU and the CPU compete for a shared power or thermal budget. When an external display is connected directly to the MBP, the Radeon constantly pulls 20W. If not, it pulls 5W. The 15W difference is exactly the amount that the CPU uses less under constant load. Not using an external display or connecting the display via an eGPU results in ~10 - 15% better CPU performance as measured in Cinebench R20.

The tests were run with only Cinebench R20 running, configured to a minimum test duration of 10 minutes. The score in the table was the one after the last run.

Here's my data:
View attachment 883052

It seems that neither clamshell mode nor the choice power adapter matter much for constant-load performance. I have the feeling that it's a power budget more than a thermal budget, looking at the CPU temperature.

Edit: Reran the dGPU measurements and added CPU temperatures.

I believe you're correct in that the GPU and CPU compete for a shared power budget. As shown in the Intel power gadget screenshot, the CPU only seems to be pulling about 20W on average. And from iStat, the Radeon 5500M seems to be pulling 30W under load.

At least from my testing today, it was able to maintain the default clock speed under load, although it did dip to 2.2 Ghz for a hot second before going back up.

The fact that the GPU is using so much memory (as shown in the last picture) is pretty interesting to me, given that I'm not doing anything graphically intense. Once I connect the monitor, the memory is 75% full, then goes up pretty much close to 100%. Right now I just have a few tabs open in my web browser and the memory is still at around 95%. It is also pulling 20W currently.

 

[TheRealAlex]

I'm getting performance issues on the new MBP 16" (i9 2.3 GHz, 5500M 4GB) when connecting to an external monitor. As I increase the workload (CPU only heavy tasks), the laptop gets slower and slower, to the point that it throttles to as low as 1.9 GHz. The thermals remain constant at around 75 - 80 degrees celsius, and the fans are at full blast. Meanwhile, when the external display isn't connected, I maintain about 2.8 Ghz, with the thermals being slightly warmer, but never above 90 degrees. I understand that there should be some performance degradation due to powering the monitor, but it can't be this bad right?

I uploaded two screenshots of intel power gadget which shows the beginning of the workload. The first one is connected to an external monitor, and the second one isn't.

Just wondering if this is normal, or if there's anything that can be done about it.

Thanks!

These i9 MAcBook Pros are unsustainable for prolonged workloads, and external monitors. Today we have 11 minute long YouTube “unboxings” Not actual work related reviews after a week hands on.

 

[x3sphere]

Interesting - I wonder if there's something wrong with how macOS is handling the clock speeds / power states for these GPUs. Doesn't seem like it should be necessary for the GPU to pull 20W just because an external monitor is connected.

Running an external display shouldn't be very demanding, especially if you aren't using scaling. I don't see why it should use much more wattage than what it takes when you're using the built in display.

 

[freitz]

This is troubling. Was about to jump on one of these for a desktop travel station

 

[seangrimes590]

I am not having this problem using an external 4K and the internal monitor at the same time (my work setup 10-12 hours a day as a CS Ph.D. candidate). Both scaled to non-integer scaling resolutions. Note, I'm not saying this problem doesn't exist, just that it's not a problem for *everybody*. My external is running off a USB-C to DisplayPort cable if that makes any difference. Relatively old, non HDR monitor. Old enough that the HDMI port doesn't accept 4K 60hz, only the DisplayPort works at 60hz.

 

[swaggypee]

Interesting - I wonder if there's something wrong with how macOS is handling the clock speeds / power states for these GPUs. Doesn't seem like it should be necessary for the GPU to pull 20W just because an external monitor is connected.

Running an external display shouldn't be very demanding, especially if you aren't using scaling. I don't see why it should use much more wattage than what it takes when you're using the built in display.

Yeah, I agree with everything you said.

So I figured that the GPU should pull less W if it drives a weaker display right? I did some more quick testing, but all these are in idle states:

Dell monitor (3840x1600 resolution): 19.4 W
1080p TV (1920x1080 resolution): 18.4 W
Not as relevant but for the curious: No display, just the laptop itself forced into GPU mode w/ GFXstatus and @ native resolution (3072x1920): 4W

I am not having this problem using an external 4K and the internal monitor at the same time (my work setup 10-12 hours a day as a CS Ph.D. candidate). Both scaled to non-integer scaling resolutions. Note, I'm not saying this problem doesn't exist, just that it's not a problem for *everybody*. My external is running off a USB-C to DisplayPort cable if that makes any difference. Relatively old, non HDR monitor. Old enough that the HDMI port doesn't accept 4K 60hz, only the DisplayPort works at 60hz.

Interesting, do you think you could post the iStat/Intel Power Gadget results? I'd be pretty interested in looking at it. Thanks!

 

[alfogator]

I normally use an eGPU but after reading this was curious, so I disconnected the eGPU and switched to discrete graphics and the Radeon power draw went to about 4W, as soon as I connected the external display it jumped to 18-19 W.

 

[MrGunnyPT]

Are you running in clamshell mode? Found it runs much cooler when connected to an external display with the lid closed.

I did not notice this on the i7 model with my 3440x1440 display, and I was running it at 120 Hz. Returned it for an i9 though. Will test when it arrives on Wed

I have tested the same with an ultra wide.

When the lid is open the computer generates around 8 to 12c more... It's ridiculous
[automerge]1576570667[/automerge]

Interesting - I wonder if there's something wrong with how macOS is handling the clock speeds / power states for these GPUs. Doesn't seem like it should be necessary for the GPU to pull 20W just because an external monitor is connected.

Running an external display shouldn't be very demanding, especially if you aren't using scaling. I don't see why it should use much more wattage than what it takes when you're using the built in display.

Yeah.. Plus you can't use the Intel UHD graphics instead for external display.. it forces you using the dGPU... The most ridiculous thing however it's the wattage that it extracts from the GPU with either using a 4k or 1080p screen.. As long as the lid is open it's 18w for both? WTF

 

[swaggypee]

I have tested the same with an ultra wide.

When the lid is open the computer generates around 8 to 12c more... It's ridiculous
[automerge]1576570667[/automerge]


Yeah.. Plus you can't use the Intel UHD graphics instead for external display.. it forces you using the dGPU... The most ridiculous thing however it's the wattage that it extracts from the GPU with either using a 4k or 1080p screen.. As long as the lid is open it's 18w for both? WTF

Well..there is a rather complicated way to disable the GPU if you don't plan on using it..but I've only seen people do it for the 2011 MacBook Pro, but I'd be very interested if anyone has tried with the 2016+ models.

I also just looked at the power draw in clamshell mode, and it's 5-6W, so as x3sphere mentioned, it should be much cooler. I'll probably do some more testing working in clamshell mode later.

Also I still have the previous 15" 2019 MBP as well that I was planning on selling, so curiosity got the better of me and I installed iStat as well to see what numbers were being shown. So this is for the MBP w/ the Radeon 560x.

For those who don't want to look at the pictures, it shows the Radeon 560x pulling just 12W on a 3840X1600 display (in idle state), and 4.3-4.4W in clamshell mode (which isnt shown in the pictures). In addition, it seems more efficient at using the video memory, with ~15% usage.

 

[seangrimes590]

Interesting, do you think you could post the iStat/Intel Power Gadget results? I'd be pretty interested in looking at it. Thanks!

Okay, so in fairness, I'll eat my words a bit. There is a noticeable difference in CPU power draw and frequency when connecting my external display. However, it's nowhere near as bad as OP is experiencing or what a few other comments have mentioned.

Attached are 4 images showing the power draw and frequency during an h265 to h265 handbrake conversion. The second pair of pictures shows running on the iGPU and internal display. The first pair show running off the dGPU with the internal display and an external 4K USB-C to DisplayPort display connected. After connecting the external display the CPU frequency goes from 3.4ghz average to 3.0ghz average. Additionally the CPU seems to be allowed to draw 18-22watts less power when the dGPU is active which is entirely consistent with dGPU power draw. Interestingly, lowering my screen brightness to near 0 allowed the CPU to draw an extra 3-4 watts. I believe this is a power delivery issue rather than a heat issue. As noted in the iStat images the system power draw is the same iGPU vs dGPU, and remains the same when lowering screen brightness. In all cases the battery is making up some of the power requirements. I am using the included charger with a grounded extension.

 

[freitz]

Is this a wide spread issue or just some people have this issue?

 

[obargy]

I'm not experiencing this at all when connecting my 16" MBP to a LG UltraFine 4K monitor in clamshell mode. In fact, I think the performance is even better than using it standalone on a flat desk.

I think it's very important to put the MBP in a vertical stand where the MBP's vent sink could face towards nothing, making it easier for hot airflow to blow out. Putting the MBP flatly on a desk would have worse ventilation than putting it vertically since your desk surface will kind of block the exhaust airflow. You could easily notice this when your desk starts to warm up : )

 

[swaggypee]

Is this a wide spread issue or just some people have this issue?

I think it isn’t so much as “issue“, but more as to whether it fits your use case. I think what we can all agree on is that there’s a shared power limit between the GPU and CPU, and that the GPU will pull ~20W, and maybe more, depending on what you’re doing. If the MBP reaches its max W (which seems to be ~65W), it will draw less power from the CPU first. Also, what nethead and seangrimes590 has shown should be a good representation of the performance you should be expecting. Again, it depends what exactly you’re using the MBP for.

Also, in an earlier post you said that you wanted a desktop travel station. You could go around the power requirements by putting an iPad on Sidecar. I just tested it, and I’m getting around 8-16W of power draw from the 5500M. Interestingly, you could also force it to use the iGPU (which I also just tried, and works) if you need more performance

 

[freitz]

will probably go 4K+. Dual monitors. Not sure if that would be an issue

 

[swaggypee]

The best way to know is just to buy it and test it yourself. If there’s an issue, you have more time right now to return it because of the holiday season.