Problem with Dell U2715H on Mac Mini

[Hrothgar]

I just bought Dell U2715H display for my Mac Mini -- based on many reviews that said this is a great display for Macs. Including a review on the Amazon page for this display.

But when I connected it, it keeps blacking out and switching resolutions. It works for about five seconds, then goes black, comes back at a higher resolution for a second, goes black, then comes back at the original resolution. I can't find any settings that solve the problem.

It's connected with the mini-Display Port in the Mini's TB port, to the full DisplayPort plug into the Display?

And, when I went to Dell's support site for this display, the listed operating systems are all Windows!
Do I just need to return this because it doesn't work on Mac OS? That would surprise me, given that reviews I've seen claiming this works great with Macs. And the display's page on Amazon does not say it's incompatible with Mac or other list the necessary operating systems.

I called Dell, and they said that the display should work fine, without any additional drivers. But they couldn't give me any other advice because I'm at work, and the monitor is at home.

Any thoughts?

 

[Fishrrman]

I'd try a different cable first...

 

[Kaida]

I had that problem with the U2412hm. Only happens on Mini DP to DP and not HDMI. Every now and then the mini would flicker/boot to in 640x480 and then change to 1920x1080. Sometimes it stays at 640x480.

I thought it was the mini being not compatible with the Dell Ultrasharp. But it also happened on my work X230 mini DP using another U2414hm and another mini dp to dp cable at work.

Solution: unplug the power. Let the capacitors discharge a little, then plug it in and restart the monitor. If the DELL logo comes on, it will be ok. If the logo doesn't come on, unplug and try again..

After a while, I gave up and bought the Samsung S27D590P for work S24E390HL for home. Works perfectly with HDMI AND mini DP to HDMI.

 

[Hrothgar]

Thank you. I guess I can also try using a mini DP to mini Dp connection?
Is this the type of problem where it might work for a while and then suddenly stop working? And I'll have to unplug/replug again?

 

[dugbee]

Funny thing is my work MBP does the same thing on my Dell. Switched to an HDMI cable and it never blinks, but I've yet to try a mini-DP to mini-DP.

 

[jpietrzak8]

Hey, dunno if this will help, but there's an option in the Dell on-screen display menu to switch on/off DP 1.2 support on the monitor. You can find it under the "Display" tab. Disabling DP 1.2 might make the monitor work better with your Mac when using a mini-DP cable...

 

[Hrothgar]

i may have found my problem:
I have my Samsung tv connected to the Mini with an HDMI cable.
I think that is screwing up the Dell when I connect it with the DP.
Should i be able to connect them both at the same time?

 

[jpietrzak8]

Should i be able to connect them both at the same time?

Yes, absolutely; all recent Minis (certainly all that were made with mini Displayport or Thunderbolt ports) are able to drive two monitors at once. I'm using a dual monitor setup with my Mini right now.

 

[Hrothgar]

so, now i'm guessing that the problem is the Mini sending conflicting signals out the DP port and the HDMI port at the same time. Should the Mini be able to identify the two different types of displays on the two different ports? Is there a setting I need to check? I don't see many options in Displays under System Preferences

 

[jpietrzak8]

so, now i'm guessing that the problem is the Mini sending conflicting signals out the DP port and the HDMI port at the same time.

I'd be surprised if that were the case; I've got two monitors hooked up to my Mini as I write this, one on the HDMI port, one on the Mini Displayport port. No problems here.

I guess the easiest way to test would be to simply disconnect the HDMI cord, and see if the problems with the Mini Displayport connection go away...

 

[Hrothgar]

I've still got the same problem. The Dell monitor works fine, as long as I unplug the HDMI leading to my tv. If I plug in the HDMI, the Dell starts up -- it seems to be changing resolutions. and when I go into "Display" under my system preferences, it seems that the Mini doesn't realize it's got two different monitors attached. I don't see any place to set the output for the specific ports (HDMI, Thunderbolt). Any ideas?

If I go into Displays under System Preferences, I see two display dialogues -- one for the Samsung and one for the Dell. Under Display "Optimize for", I try to set the Samsung to "Samsung" and the Dell to "U2715h". But the computer sets them both for the same optimization. So, they're either both set to optimize for the dell or both for the Samsung.

Any ideas? This doesn't seem right.

 

[jpietrzak8]

Under Display "Optimize for",

Ahah! You've got "Mirroring" turned on. That should probably be turned off; you should be able to find a toggle to turn mirroring on or off under the "Arrangement" tab for one of the two display dialogues. Hopefully, that'll fix the problem; odds are that neither of them wants to support the optimal resolution of the other. (And I'm not sure why you'd even want mirrored displays in your particular setup...)

 

[Hrothgar]

I thought I wanted "mirroring" on -- I want each monitor to have the same image. If I turn off mirroring, wont the two monitors act as "linked" -- "extended desktop"?

 

[jpietrzak8]

I thought I wanted "mirroring" on -- I want each monitor to have the same image. If I turn off mirroring, wont the two monitors act as "linked" -- "extended desktop"?

Er, why would you want them to have the same image? The Dell is (probably) going to have a much higher native resolution, and is probably smaller physically than your TV. (I guess this depends a lot on your TV.) And, there's that "overscan" thing that you've always gotta mess with on a TV, but makes no sense on a normal monitor. It'll be difficult to display the same data on both.

And really, what is the point of doing so? I only see mirroring of value if you're trying to display information to an audience; unless you're trying to get someone else to see the same data you're looking at, and that someone else can't look over your shoulder, I don't see why you'd want to bother...

 

[Hrothgar]

I used to use the Samsung as the display before I bought the Dell. I was using the Mini "headless", and only need the Samsung display every now and then. Now, I'll use the Dell display almost exclusively. But I suspect there will be times when I want to play a movie off my Mini or perhaps watch Youtube videos from the Mini on the Samsung. But, you're correct that I generally will not need both monitors at the same time.

However, it still irks me that this isn't working. Everything I read suggests that this should work. The problem seems to be that Mini wont set the Samsung to optimize for Sumsung and at the same time set the Dell to optimize for Dell. That seems odd. I assume the Mini is supposed to be able to optimize for two different monitors at the same time. But maybe not.

I'll to "unmirror" them and see if that solves the problem.

 

[jpietrzak8]

The problem seems to be that Mini wont set the Samsung to optimize for Sumsung and at the same time set the Dell to optimize for Dell.

This is very likely because the Samsung is a TV and the Dell is a monitor. Odds are good that the optimal setting for the Samsung involves some odd variables (like "overscan"), and the optimal setting for the Dell involves a resolution that is impossible for the Samsung to display.

If you want mirroring to work, you'll need to choose a set of options that are shared between both displays; that is, settings that are not optimal for either monitor. The "lowest common denominator".

Honestly, there is absolutely nothing wrong with using an extended desktop. With that, you can even play videos on one monitor while doing work on the other!

 

[Hrothgar]

Thank you. The Mini can't handle different settings for the HDMI port v. the Thunderbolt port? Shame.

So -- I'd been having trouble registering the Monitor with Dell. It kept asking me for information to transfer the warranty. I finally got through to a customer service person and they told me that the monitor is already registered to someone else. I bought the monitor from Amazon, but the seller was a third-party, Mega Supply. Dell wouldn't tellm e who the owner was, but said is wasn't Mega Supply. So, I'm guessing that someone had this monitor, registered it and then returned it for whatever reason.

Amazon will give me a refund, but it's a pain because I no longer have the box.

Any thoughts on whether I should get the same monitor directly from Dell? The price has dropped by $60. Or is there a better alternative?

 

[jpietrzak8]

Thank you. The Mini can't handle different settings for the HDMI port v. the Thunderbolt port? Shame.

Ok, now I'm REALLY confused. You are the one who said you wanted mirroring. Let me state this explicitly:

When you "mirror", you use the SAME settings for both monitors. That's the whole point of "mirroring" -- you present the exact same picture to both monitors.

It is only when you use an "extended desktop" that you even have the ability to provide different settings for different monitors.

In short -- your Mini is not providing different settings for the different ports, because you are TELLING your Mini not to provide different settings for the different ports!

 

[Hrothgar]

No, I'm the one that's confused. I do (did) want to mirror the displays. I thought that the Mini would be able to send out an optimized Samsung signal through the HDMI at the same time it sent an optimized Dell signal through the Thunderbolt for the same picture to appear on each monitor. If it can't, that's fine.

Thanks again for all the help.

 

[jpietrzak8]

I thought that the Mini would be able to send out an optimized Samsung signal through the HDMI at the same time it sent an optimized Dell signal through the Thunderbolt for the same picture to appear on each monitor. If it can't, that's fine.

In theory, you could do something like that; but you'd have to do significant work to pull it off. Graphical applications are incredibly sensitive to the amount of available screen space. Many apps have icons or other graphical features that are of a fixed size, so that you can only display a fixed number of them in a given amount of space; others feature multiple screens or interactive widgets, which may need to be displayed differently or hidden if not enough space is available.

In short, each application would have to treat each monitor as a completely different display in order to take advantage of the different screen space available. Which kind of defeats the purpose of showing the "same" screen on both monitors.

Of course, you could do this another way: you could take the resolution of one of the two screens, and tell the apps that _both_ screens have that resolution. Then, pipe the properly-sized screen to the one monitor, and an up-sized or down-sized screen to the other. The second monitor won't look perfect, but it'll at least it'll match the first one. Which is basically what Apple has chosen to do in this case.

 

[Hrothgar]

So -- same problem when I turn on the mirroring.
Still not sure why it doesn't work. Maybe it would work with two monitors, but not with a monitor and a tv.

 

[jpietrzak8]

So -- same problem when I turn on the mirroring.
Still not sure why it doesn't work. Maybe it would work with two monitors, but not with a monitor and a tv.

So, let me ask: have you tried testing mirroring with a low resolution (say, something like 1024x768)? I'm thinking that the optimum resolution for the TV is unusable on the monitor (and vice-versa). Once you find a setting that works for both, you can slowly increase the resolution until you find the place where the two devices diverge from each other.

Also, have you even once tried "extended desktop"? That allows each monitor to be independent of the other (allowing you to optimize settings for both), and it really isn't hard to use. I swear!

 

[Hrothgar]

I have tried the extended desktop -- same problems.
I haven't played around with different resolutions. I'll give that a try.
Right now, I just leave the hdmi to the Samsung unplugged. If I need it, it will be easy enough to put it back in.