XPS 15 9575 USB-C -- HDMI resolution issues

Question

Hi all. I'm trying to run my XPS 15 9575 with 4k display with an additional external 27in Dell monitor capable of 1440 X 2560 native resolution. My USB C to HDMI cable is rated at a maximum of 4k. The problem is that the laptop will only let me choose a maximum resolution of 1920x1080. The cable works ok on a MacBook Pro so I'm not sure what's going on. I can change the scaling but the display quality is garbage. Does anyone know of a fix for this?

jphughan · Accepted Answer

@eighteentee Page 3 of the U2713HM User Guide here says "Our HDMI is 1.4, it is compatible and can support up to 1920 x 1080." Normally HDMI 1.4 supports up to 2560x1440, so that sentence is odd, but it seems like there might be a limitation on the HDMI input of the display. If you can run 2560x1440 from your MacBook Pro using the same cable, I'm not sure how to account for that other than a possible interoperability issue with that system and that USB-C to HDMI cable. I've seen issues with USB-C to HDMI cables/adapters on multiple occasions on this forum, and I think it's because USB-C to HDMI requires incorporating an active signal converter chip to switch the DisplayPort signal coming out of the USB-C port over to HDMI, and active signal converter chips introduce complexity, which can create problems even when they shouldn't exist. I've had multiple cases here where someone will report that their USB-C to HDMI adapter/cable works fine with certain source devices but not others, and every single time I've suggested that the person try a different brand of cable/adapter, the user has reported back that the alternative brand resolved the issue with the problematic source while maintaining compatibility with the other source. Obviously that shouldn't be necessary, but it's also true that not everything that should work in the tech world always does.

Anyway, in your case I'd recommend getting a USB-C to DisplayPort cable instead. That way you won't have a signal converter chip to deal with at all, since that cable will just be able to pass the native DisplayPort signal coming out of the system, which is much simpler. And then you won't have to deal with the limitation mentioned in the display's documentation since you'll be using its DP input instead.

eighteentee · Answer

No, not quite. The display on the laptop is 4k but the 27in Dell display I'm connecting to is 1440x2560 The 27in Dell monitor is a U2713HM

jphughan · Answer

@eighteentee  I'll assume you're going for 4K 60 Hz here rather than 4K 30 Hz.  Is the USB-C to HDMI cable plugged directly into the system, not going through any sort of multi-purpose adapter?  How is the additional 27' display connected?  What exact 4K display are you using?  Some early 4K 60 Hz displays only support 4K 60 Hz on their DP inputs because 4K 60 Hz support on HDMI didn't arrive until HDMI 2.0 and those displays were created before HDMI 2.0 existed.  In that case, the cable's rating is meaningless.  The more details you can provide about exactly what equipment you have and how it's all connected, the more likely people here who are willing to help will be able to give you useful guidance.

eighteentee · Answer

I was beginning to think I was going mad! Yes it does seem odd. I was going for HDMI as I use a pair of these monitors connected to a Mac Pro (not the MacBook Pro - I was just testing that) using display port. Using HDMI I could avoid unplugging the display port cable from the monitor every time I want to connect the XPS to it. I have seen USB C to DVI cables that supposedly run at 2560x1440 but conflicting notes in the monitor manual describe the DVI port as just a DVI Dual Link port and label it as it as just DVI. I honestly don't know do to tell the difference between a standard DVI cable and a Dual Link DVI cable - they look both the same to me!

jphughan · Answer

@eighteentee Aha, you didn't mention that the Mac scenario that was working involved using a different input. For future reference, when asking for technical assistance, providing that sort of detail is helpful, as it can save a lot of time going down the wrong path.

Dual link DVI cables require a full set of pins, except for the four pins around the corners of the "bar" portion of the connector, which are used for carrying VGA. Single link DVI cables are allowed to omit some of the pins in the center of the connector. However, USB-C to Dual Link DVI adapters are fairy rare and rather expensive, just as Mini-DisplayPort to Dual Link DVI adapters were back in the day. StarTech and Club3D make them, though. But if you just find a USB-C to DVI cable that has a full complement of pins in its DVI connector, I would absolutely NOT assume that it will support dual link DVI.

But if you want to go that route, checking over the User Guide again, it does appear that the display supports dual link DVI. On Page 11, the description of the DVI connector mentions the importance of using dual link DVI cables multiple times. And on Page 14 under Physical Characteristics, the DVI connector is specifically described as DVI-DL. But perhaps best of all, this thread has confirmation from actual real world use indicating that the U2713HM can run 2560x1440 from dual link DVI. I'll take real world confirmation over documentation any day.

eighteentee · Answer

Unbelievably, there is a happy ending to this story. I took a gamble and bought an inexpensive USBC to DVI cable from Amazon. It works! Full 2560x1440 at 59hz!

XPS

XPS 15 9575 USB-C --> HDMI resolution issues

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