Do you have the system's AC adapter connected? It's hard to tell from the limited specs on the Samsung CJ890's product page, but it mentions something about offering power over USB-C. If it does, then that's your issue, because the XPS 15 systems require 130W of power for proper operation, and the official max of the USB Power Delivery spec is 100W, although most displays will only supply 45-60W. If the system is connected to an undersized power source, it will throttle performance before trying to make up the power deficit on the battery because it assumes that you want it to at least try charging the battery or maintaining its charge level, even if that means throttling -- because if it was configured to run at max performance even if that meant drawing on the battery while plugged in, it might ultimately drain the battery entirely, and then you wouldn't be able to keep using the system at all anymore until you connected an appropriate power source.
The only way to charge an XPS 15 properly over USB-C while it's running is to use a Dell dock like the WD15 or TB16, because Dell has some done something proprietary there to push 130W over a USB-C/Thunderbolt 3 cable. But even there, with the WD15 you'd need the version that comes with the 180W AC adapter, and with the TB16 you'd need the version that comes with the 240W AC adapter. Both of those dock models are also available with lower-wattage options for use with systems that don't require as much power. Otherwise, if you also connect your system's AC adapter, you should be fine.
If you still have problems, the XPS 15 will throttle even with a proper power source when it is under heavy load, especially when both the CPU and discrete GPU are busy. That is a product of the fact that it is designed to be a thin and light system, which means it doesn't have a sufficiently robust cooling system to run at max load for sustained periods of time. Most thin and light systems throttle to some extent due to this design decision. People who need to run at max load without throttling need to look at chunkier laptops that have more cooling capacity.
But either way, you should also reverse the change you made to the processor minimum state. Setting that to 50% rather than the default 0% will only force your CPU to run faster than it actually needs to, which means you'll just be missing out on battery life. It will NOT prevent the system from throttling due to temperature and/or power deficits, since that is enforced by the firmware.
Lots of pixels on Samsung CJ890 to drive - 3840x1200 if 43", 3840x1080 if 49".
You might try just the HDMI connector, it might only run at 30 Hz, but might work or isolate any power issues (laptop might be confused and think it's getting power over USB-C, since the CJ890's two USB-C ports support powering the devices connected to it. Not sure it would make a difference, but the monitor does support dual inputs to create a seamless dual monitor configuration - so, maybe: HDMI (1920x1200) + a USB-C (1920x1200 - maybe with a USB-C to DisplayPort adapter if power over USB-C is an issue).
I'd google other users trying to get dual monitor, 4k or 5k external monitor(s) working with the Dell XPS 15 9550 - they likely would have similar issues to yours.
Terrific reply, thank you very much. I have read and applied it. I can confirm that it has been resolved. I will keep the power supply plugged in from now on.
Lots of pixels on Samsung CJ890 to drive - 3840x1200 if 43", 3840x1080 if 49".
You might try just the HDMI connector, it might only run at 30 Hz, but might work or isolate any power issues (laptop might be confused and think it's getting power over USB-C, since the CJ890's two USB-C ports support powering the devices connected to it. Not sure it would make a difference, but the monitor does support dual inputs to create a seamless dual monitor configuration - so, maybe: HDMI (1920x1200) + a USB-C (1920x1200 - maybe with a USB-C to DisplayPort adapter if power over USB-C is an issue).
I'd google other users trying to get dual monitor, 4k or 5k external monitor(s) working with the Dell XPS 15 9550 - they likely would have similar issues to yours.
A few things here:
- Running 4K 60 Hz isn't the issue. I can run that on my even older XPS 15 9530. See my post above.
- Most displays that have multiple inputs do not support using them simultaneously, with each input only driving a portion of the display. But even if they did, a 4K display area is 4x 1080p, so 2x 1920x1200 would only fill half of it -- or technically slightly more than half if the display is 3840x2160 and your "panels" are 1200 pixels tall.
- 5K resolution is a whole other animal. That would require a single DisplayPort 1.3 or better channel, or else Thunderbolt 3, which can carry up to two full DisplayPort channels, and 2x DP 1.2 has enough bandwidth for that. There are some problems there. First, no Intel GPUs currently on the market support anything newer than DisplayPort 1.2 for external display outputs (they can do better than that on embedded DisplayPort for built-in panels), and second, no Intel GPUs currently on the market support 5K resolution. That's normally a problem because even among laptops that have discrete GPUs, most of them have all of their display outputs physically wired to the Intel GPU for technical reasons I can explain if you're actually curious -- which means 5K resolution is off the table. There are a few laptops that have outputs wired to the discrete GPU instead though, typically gaming laptops and professional workstation models. If you had a laptop that had a sufficiently high-bandwidth display output wired to its discrete GPU and the discrete GPU supported 5K, you could run 5K. The Precision 7x20 and 7x30 models can do this, for example. But they are part of a very small club.
jphughan
9 Legend
•
14K Posts
1
December 10th, 2018 07:00
Do you have the system's AC adapter connected? It's hard to tell from the limited specs on the Samsung CJ890's product page, but it mentions something about offering power over USB-C. If it does, then that's your issue, because the XPS 15 systems require 130W of power for proper operation, and the official max of the USB Power Delivery spec is 100W, although most displays will only supply 45-60W. If the system is connected to an undersized power source, it will throttle performance before trying to make up the power deficit on the battery because it assumes that you want it to at least try charging the battery or maintaining its charge level, even if that means throttling -- because if it was configured to run at max performance even if that meant drawing on the battery while plugged in, it might ultimately drain the battery entirely, and then you wouldn't be able to keep using the system at all anymore until you connected an appropriate power source.
The only way to charge an XPS 15 properly over USB-C while it's running is to use a Dell dock like the WD15 or TB16, because Dell has some done something proprietary there to push 130W over a USB-C/Thunderbolt 3 cable. But even there, with the WD15 you'd need the version that comes with the 180W AC adapter, and with the TB16 you'd need the version that comes with the 240W AC adapter. Both of those dock models are also available with lower-wattage options for use with systems that don't require as much power. Otherwise, if you also connect your system's AC adapter, you should be fine.
If you still have problems, the XPS 15 will throttle even with a proper power source when it is under heavy load, especially when both the CPU and discrete GPU are busy. That is a product of the fact that it is designed to be a thin and light system, which means it doesn't have a sufficiently robust cooling system to run at max load for sustained periods of time. Most thin and light systems throttle to some extent due to this design decision. People who need to run at max load without throttling need to look at chunkier laptops that have more cooling capacity.
But either way, you should also reverse the change you made to the processor minimum state. Setting that to 50% rather than the default 0% will only force your CPU to run faster than it actually needs to, which means you'll just be missing out on battery life. It will NOT prevent the system from throttling due to temperature and/or power deficits, since that is enforced by the firmware.
Techgee
2 Intern
•
623 Posts
0
December 10th, 2018 08:00
Lots of pixels on Samsung CJ890 to drive - 3840x1200 if 43", 3840x1080 if 49".
You might try just the HDMI connector, it might only run at 30 Hz, but might work or isolate any power issues (laptop might be confused and think it's getting power over USB-C, since the CJ890's two USB-C ports support powering the devices connected to it. Not sure it would make a difference, but the monitor does support dual inputs to create a seamless dual monitor configuration - so, maybe: HDMI (1920x1200) + a USB-C (1920x1200 - maybe with a USB-C to DisplayPort adapter if power over USB-C is an issue).
I'd google other users trying to get dual monitor, 4k or 5k external monitor(s) working with the Dell XPS 15 9550 - they likely would have similar issues to yours.
XPS9550-USBC
2 Posts
0
December 10th, 2018 08:00
Terrific reply, thank you very much. I have read and applied it. I can confirm that it has been resolved. I will keep the power supply plugged in from now on.
jphughan
9 Legend
•
14K Posts
0
December 10th, 2018 09:00
A few things here:
- Running 4K 60 Hz isn't the issue. I can run that on my even older XPS 15 9530. See my post above.
- Most displays that have multiple inputs do not support using them simultaneously, with each input only driving a portion of the display. But even if they did, a 4K display area is 4x 1080p, so 2x 1920x1200 would only fill half of it -- or technically slightly more than half if the display is 3840x2160 and your "panels" are 1200 pixels tall.
- 5K resolution is a whole other animal. That would require a single DisplayPort 1.3 or better channel, or else Thunderbolt 3, which can carry up to two full DisplayPort channels, and 2x DP 1.2 has enough bandwidth for that. There are some problems there. First, no Intel GPUs currently on the market support anything newer than DisplayPort 1.2 for external display outputs (they can do better than that on embedded DisplayPort for built-in panels), and second, no Intel GPUs currently on the market support 5K resolution. That's normally a problem because even among laptops that have discrete GPUs, most of them have all of their display outputs physically wired to the Intel GPU for technical reasons I can explain if you're actually curious -- which means 5K resolution is off the table. There are a few laptops that have outputs wired to the discrete GPU instead though, typically gaming laptops and professional workstation models. If you had a laptop that had a sufficiently high-bandwidth display output wired to its discrete GPU and the discrete GPU supported 5K, you could run 5K. The Precision 7x20 and 7x30 models can do this, for example. But they are part of a very small club.
Techgee
2 Intern
•
623 Posts
0
December 10th, 2018 12:00