MacBook Pro with Dell 4K P2815Q and SwitchResX

I have tried with and without SwitchResX, and it works but you don't need it (at least on my mid 2012 Mac PowerBook Pro).

To use the Dell P2815Q on the MPB Pro, open the System Preferences / Displays

Hold down the Option key and click Scaled

Enable: Show low resolution modes

Select a resolution that you like that indicates low resolution

If you select 2560 x 1440 (low resolution) you will see the same screen size as a Thunderbolt monitor

The low resolution mode responds faster than HiDPI (which is the default)

Cursor handling, screen refresh and sharpness are all acceptable and usable at this setting.

Hi Thanks for this valuable info. Please let me know what is the refresh rate when it is on 2560x1440? Can we get 60Hz? Thanks!!!

The P2815Q will still be running at 30 Hz refresh rate even at 2560x1440 (HiDPI or Low Resolution). If you want the P2815Q to run at 60 Hz, you will have to lower the resolution to 1920x1200 or lower. This is a limitation of the display, not the computer. In most cases, 30 Hz is not a problem. The cursor lag that users discussed is not a result of the refresh rate, it's a result of inadequate graphics performance in the computer. That is why I eventually purchased a Dell U2714H display (2560x1440, 60 Hz) and it works much better on my Mac Mini (2014) and on my MacBook Pro (2012). I should point out that the Mac Mini (2014) does work in 4K mode with the Dell P2815Q (and looks great), but I can't bear the tiny fonts, even with my new reading glasses. With the Mac Mini attached to the P2815Q, I can set it for 2560x1440, 30 Hz, but only in Low Resolution mode, not HiDPI mode. SwitchResX cannot fix that.

I am now using the P2815Q on my ASUS Windows 7 (2010) laptop that can only display as high as 1920x1200, 60 Hz. I will someday get a newer computer that can properly handle the 4K display mode on the P2815Q. With an appropriate graphics card such as in a Mac Pro, the P2815Q will be able to display 2560x1440, 30 Hz in HiDPI mode and it will look great and will respond great. I tested it on a friends Mac Pro 2014.

I admit that 60 Hz is better than 30 Hz, but I don't believe it's as bad as some users make it out to be. I have recently realized that one of my televisions only runs at 720p 30 Hz, and it's fine for watching the shows that I view using Apple TV or Cable.

Another note: I found SwitchResX to be very sophisticated but unnecessary. I prefer "Display Menu" by Thorsten Karrer. It's much easier to use and with the $2 in-app upgrade purchase it will quickly help you select the HiDPI modes that your displays support. It's especially nice when using both displays (U2174H and P2815Q) simultaneously on my Mac Mini.

Hey joebinis,

Thank you very much for your revealing and comprehensive explanation! However, I think you are referring to your U2713HM that features 1440p/60Hz?

Thanks for the note. I did type the display model incorrectly. I am using the Dell U2715H display at 2560x1440, 60 Hz.