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XPS 15 9560, WD15, Dual screen 144Hz + 60Hz
Hi folks
I'm using my XPS 9560 docked to a WD15.
I just buy an Asus VG248QE monitor in order to use it at 144Hz.
But I'm using a dual screen system.
With a mDP I'm plugging the 144Hz, and with a VGA or HDMI I'm plugging an other Asus monitor, but running at 60Hz.
When using the 144Hz monitor alone, I've no problem for the framerate that I can set in intel graphics settings.
However, when I'm using both monitors, they're running both at 60Hz and I'm not able to set the 144Hz mode on the matching monitor.
As I read some informations on Internet, I'm not sure if it's a Windows 10 issues preventing from using different framerates for differents monitors (in that case I wouldn't know how to fix the problem as it seems to need the Nvidia graphics display settings to solve), or if it's a limitation coming from the XPS 9560 &/or the WD15 ?
What do you think about it ?
Thanks a lot
(I think I saw some posts from @jphughan talking about this ?)
jphughan
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July 25th, 2018 16:00
It's a bandwidth issue. As shown here, the WD15 can only handle dual 1080p displays at 60 Hz, or a single 1600p display at 60 Hz, or a single 4K display at 30 Hz.
That's related to the fact that USB-C currently only supports DisplayPort 1.2 rather than the faster 1.3+ standards and because when USB-C is being used for display output and USB data simultaneously (as is the case with a dock like the WD15), then you only get half the bandwidth of a full DisplayPort link. You can either connect one of your displays to the XPS 9560's HDMI port so your USB-C output only has to drive one display, or you can get a dock like the TB16 that uses Thunderbolt 3 rather than USB-C. That means it gets two full DP 1.2 links, which means 4x the display bandwidth available. I wrote a long technical thread about USB-C and TB3 that explains all of this in more detail here if you're interested. Also note that if you get the TB16, in order to use it with the XPS 15 9560 you'll need the version that comes with the 240W adapter.
Dji_AC
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July 25th, 2018 16:00
I manage to have a first answer by plugging my second monitor in HDMI with the port directly on the 9560 and then I have the dual monitors with dual framerate without any trouble, at desktop without game or application.
I guess it's the WD15 that's limiting with its bandwitch then ?
But what other dock station can I take with the XPS 9560 ?
Dji_AC
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July 25th, 2018 23:00
Thanks for your detailed answer as always !
Just a question about the TB16.
When I was looking at the dock I was going to buy, I remember reading troubles for some of the Thunderbolt version of the docks, maybe it was the TB16.
Are you aware of any trouble coming from the thunderbolt dock of Dell ?
@jphughan
Dji_AC
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July 26th, 2018 01:00
I just read a ton of bad users stories for the TB16, not encouraging :/
Maybe I should watch for competition dock instead :/
jphughan
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July 26th, 2018 06:00
In fairness, there are plenty of threads about problems with the WD15 as well. The reality is that people are far more likely to post threads about problems than to say, "Everything is working great", so if you go looking for problems on any product that's relatively widely used, you're likely to find them. I've personally never had a problem with the WD15 or the TB16. A friend of mine ran into a known issue that occurs when an old version of Citrix Receiver is installed, but that was solved by updating to a newer version of Citrix Receiver. Some people who use BitLocker are annoyed that if you configure the BIOS to allow keyboards attached via the TB16 to work at boot, then you'll end up seeing the Recovery Key prompt whenever the dock connection state changes compared to the previous boot. That's the result of technical details about Thunderbolt and deliberate security measures related to BitLocker, although I've read that an updated Thunderbolt controller/standard may offer a solution there.
As for the competition, you're unlikely to ever find a third-party dock that will properly charge your XPS 15 because that system requires 130W for full performance, which is above the 100W official max of the USB Power Delivery standard. Dell is doing something proprietary there to exceed the standard, and in fact most third-party Thunderbolt docks still only deliver 60W (so they don't have to step up to special cabling and chips required to exceed 3 amps at USB PD's 20V), with a few capable of 87W to support the MacBook Pro. You could of course wait for a next-gen Thunderbolt dock from Dell I guess, but personally if this display issue bothers you, I'd just buy the TB16 to see how it goes. You can always return it.
Dji_AC
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July 26th, 2018 08:00
Thanks for your answer again.
For now the solution with the second monitor plugged directly on the laptop is working, I'll try to find a "cheap" TB16 to test everything :)
jphughan
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July 26th, 2018 10:00
You're welcome, and good luck. I've seen used TB16s for sale without an AC adapter, so if you can find one of those and then buy a Dell 240W AC adapter separately, you'd be in business.