Macbook Pro 13” with a 4K monitor at 60Hz 2560 x 1440 success

Sandy944

macrumors newbie
Original poster
Mar 26, 2019
3
1
Hardware: Macbook Pro 13” Retina late 2013, Monitor 4K, 27” BenQ PD2700U
Software: SwitchResX http://www.madrau.com

Result/Bottom line: Using SwitchResX software allowed me to use 2560 x 1440 resolution at 60Hz refresh rate and the monitor kept the sharpness and detail of the full 4K resolution. The mac software was stubbornly stuck at 24Hz creating tons of lag in the mouse and moving windows. The problem is a communication problem not an inherent weakness of the Mac/Intel video card.

Background: Like many I bought a 4K monitor and when I hooked it up to my Macbook Pro it could only drive it at a 24Hz refresh rate. This creates a huge lag when moving the mouse or windows. A poor user experience as Apple would say. I reduced the font size to an effective resolution of 2560 x 1440 but the refresh rate would not change. For me the native 3840 x 2160 was too small and 2560 x 1440 was my preferred scaling. I tried using the option command to get at other resolutions but the 24Hz could not be changed.

I also have HP Envy that had the same generation of Intel video card (4600) as the Mac Intel Iris Retina. On this computer setting the same external monitor to 3840 x 2160 gave me 30Hz but when I change to 2560 x 1440 I had 60Hz refresh. The resolution and the refresh rate should trade off so this made sense.

When I went into About this Mac/system report/graphics displays it listed my external monitor at 5K (which it is not) which then drove the 24Hz refresh rate. When you change the font size in the Mac video settings it keeps the 5K designation and just adds “looks like” 2560x1440.

However, when I load the SwitchResX software I can now set 2560 x 1440 actual resolution at 60Hz and there is absolutely no loss of sharpness. Looking at the El Capitan default background picture it is indistinguishable between the Mac setting of 3840 x 2160 at 24Hz and the SwitchResX setting of 2560 x 1440 at 60Hz. I even compared a 2560 x 1440 2K monitor to the 4K monitor and the 4K monitor is clearly sharper even though the font is the same size.

I used the 2560 x 1440 (NTSC) setting in the SwitchResX. I suspect the upscaling to produce the 4K sharpness is being done by the monitor instead of the Mac video card.

The SwitchResX software also provides 3840 x 2160 at 30Hz (better than 24Hz) or you can create in-between resolutions/refresh rates although I have not tried this.

It appears there is a communication short coming between 4K monitors and the Mac software and this software corrects it. Note there are other software options that allow you to choose alternate resolutions, however when I looked at SwitchResX FAQ’s I read some very through technical info on the mac video card and its limitations (165 MHz MAX resolution bandwidth). This gave me confidence that they knew what they were doing. They also stated that if you tried to ask for a setting that the video card did not support that it would just not work. I was concerned about harming the video card with an unsupported setting.

For $16 I couldn’t be happier at this point.
(I know I sound a bit like an advertisement but I did so much searching trying to solve this problem. The BenQ was a beautiful monitor and it was so disappointing to have all that lag.)
 

treekram

macrumors 68000
Nov 9, 2015
1,849
405
Honolulu HI
It would be helpful if you would tells us what OS version you're using (10.X.Y) and what version of SwitchResX you're using (even if it's the latest version, if you state the exact version, people reading this post at some future date have a reference point).
 

Sandy944

macrumors newbie
Original poster
Mar 26, 2019
3
1
Thanks for the catch. I tried to edit the original but it didn't let me so here are the versions Mac OS Mojave 10.14.3 and SwitchResX 4.8.1
 
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