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U2720Q, MacBook Pro 2013 13", using mDP to DP cable
I have a 13" Macbook Pro (Late 2013 Retina) which I want to use with Dell U2720Q. It works with Thunderbolt to HDMI and gives me a pixelated 1080p resolution. But, when I connect it using a Thunderbolt to DP cable, I get a "No DP signal from your device" message on the screen. This is the mDP to DP cable I am using. Is there a way I can get even a retina-1080p resolution with this combination? A 2k resolution would be the best, but maybe I'm expecting too much!
jphughan
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July 12th, 2020 12:00
@rgelld According to the Tech Specs page for that system here, the MBP 13" Late 2013 only supports up to 2560x1600 at 60 Hz, which suggests that it only supports DisplayPort 1.1 and therefore if you want 4K, it would only run that resolution at 30 Hz. I suspect what's happening when you run 1080p is that macOS is still sending a 4K signal across the wire and only rendering the desktop at 1080p size. Those options are there primarily for Retina displays so that you can choose where you want to land on the physical size vs. amount of workspace spectrum. But it doesn't mean that the system is actually sending a 1080p signal to the display. If you want to try to achieve that, try using SwitchResX, which gives you a lot more control over display setups in macOS.
That said, I really wouldn't recommend using a 4K 60 Hz display with a system that can't drive it properly. Best case you wasted money on technology you can't properly utilize. But chances are you'll end up worse off than that, especially if you want "2K" resolution, by which I assume you mean 2560x1440, even though calling that "2K" is a misnomer. The proper term for that is QHD or 1440p. In that scenario, you'll actually end up with noticeably worse image quality than you would have gotten if you'd simply bought a 27" 2560x1440 display in the first place, such as the U2719D. The reason is that LCD displays don't look good when driven below their native resolution, and this is especially noticeable with text. So you'll have essentially have spent more money to get a worse result. Using 1080p if you can get SwitchResX to generate that signal will be less of a problem because at least in that case, each pixel in a 1080p source signal maps perfectly onto a 2x2 pixel grid of a 4K display, so the scaling artifacts won't be nearly as bad -- though you may still see some issues due to artifacts from subpixel rendering, which is used to sharpen text. But a 2560x1440 signal does not map cleanly onto a 4K pixel grid.
rgelld
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July 12th, 2020 10:00
Update: I was able to get the cable to work by removing the other cables and holding the power button for 10 seconds. Now it works, though I only get an output at 30Hz, even though I am using a 1080p resolution. Is this a hardware limitation or is there a way I can get around it?
jphughan
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July 12th, 2020 12:00
@rgelld Happy to help, even though I'm sorry I didn't have better news. I should clarify thought that if you use SwitchResX to send an actual 1080p signal to the display, then you lose all of the benefits of having 4K pixel density. So instead of having a Retina-type experience where things are 1080p-size but really sharp, you'll have an experience where things are 1080p size and actually 1080p resolution -- and in fact 1080p resolution on a 27" display is actually noticeably below "standard" pixel density, which on macOS is 100 pixels per inch. To have 100 ppi with only 1080p resolution, your display would need be no larger than 23". That's why 27" displays are often 1440p, and the few 27" actual 1080p displays on the market are often used for kiosk type setups where size matters more than sharpness and/or for people with reduced eyesight where they just want things to be larger rather than having a larger workspace from having more resolution.
What macOS is doing right now is rendering 1080p size but still sending a 4K signal, so you're getting a very sharp version of a 1080p-sized desktop -- but since the actual resolution is still 4K, you're limited to 30 Hz.
So your only real options with that system and display pairing are:
As you can see, none of those is ideal, which is why if you can, I would strongly consider getting a U2719D instead.
But to get a true Retina-grade experience on a 27" display, you actually need 5K resolution, such as the LG UltraFine display. But you'd need a different system to drive that.
DELL-Cares
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July 12th, 2020 12:00
We tried reaching you on a private message but did not receive a response. Please feel free to reply to the private message whenever you are available.
rgelld
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July 12th, 2020 12:00
Got it, @jphughan thanks, that answers my question perfectly!
rgelld
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July 12th, 2020 21:00
@jphughanpretty cool, you know your stuff! Yes, that is what exactly what was happening. When I use the mDP to DP, I was getting 1080p but at a 4k resolution at 30Hz. Upon searching a bit, I found that I can switch the display to use a particular resolution in "low resolution" mode, so I switched to 1440p low-res mode which is at 60Hz. That being said it is still not as good as it would be on a 1440p monitor natively - exactly like you described, but it is workable. I use my old laptop just to browse the internet and watch movies etc, so I don't mind the low resolution, my internet isn't power enough to support 4k anyway. That being said my work laptop is 2018, and that works perfectly fine at the 4k resolution so that arrangement is good.
I did not know about the 5k, that is interesting, I'll certainly do some research on this! Thanks once again, hope it helps someone who is running into the same problem. The 2013 macbook pro itself is still going strong, no issues whatsoever, and so I think other people might hit this as well!