How should I calculate the possible supported resolutions of my GPU?

[rm-rf]

Hey everyone!

I would love to update my current setup and buy an ultra-wide monitor, main purpose would be work: I am a software engineer and I spend most of my time either on Visual Studio Code or in GitHub reviewing someone's code.

I narrowed down my options either to:
1) Samsung C43J890DKU - (43°) 3840 x 1200
2) Samsung LS49A950UIUXEN - (49°) 5120 x 1440

I'd love to make sure that my purchase would also work for my private laptop which is a MacBook Pro mid-2014 (Intel 2.6 Ghz I5-4278U). I did some investigation and the internal GPU (Iris 5100) seems to support up to 3200x2000@60Hz via DP and 3280x2000@60Hz via HDMI.

Now... the width is clearly less than even the 43° inches but I was wondering (and this might sound incredibly dumb), is it that I should consider? or the multiplication of 3200*2000 to get the total number of pixels? because in that case the 43 inches should work. All of that at 60Hz, otherwise I am afraid it won't feel smooth at all.

Thanks!

 

[joevt]

There's a max width and a max height. It's probably 4096 for each? 5120 is too wide for old Intel GPUs.

Seems you have a MacBook Pro (Retina, 13-inch, Mid 2014). Apple tech specs say you can do two external displays of 2560x1600@60Hz with DisplayPort and 3840x2160@30Hz or 4096x2160@24Hz.

MacBook Pro (Retina, 13-inch, Mid 2014) - Technical Specifications - Apple Support (CA)

support.apple.com

You should be able to get 3840x2160@30Hz or 4096x2160@24Hz with DisplayPort as well (maybe requires a patch)?

So I think 3840x1200 should be possible with a lower refresh rate. If the display doesn't automatically give you the lower refresh rate option, then you can try creating a custom timing with SwitchResX.

To figure out the maximum refresh rate, find the max pixel clock of the known resolutions (assuming CVT-RB timing):

edid-decode -S --cvt w=2560,h=1600,fps=60,rb=1
edid-decode -S --cvt w=3840,h=2160,fps=30,rb=1
edid-decode -S --cvt w=4096,h=2160,fps=24,rb=1
edid-decode -S --cvt w=3200,h=2000,fps=60,rb=1
edid-decode -S --cvt w=3280,h=2000,fps=60,rb=1

Result:

CVT:  2560x1600   59.972 Hz   8:5    98.713 kHz  268.500 MHz (RB)
CVT:  3840x2160   29.981 Hz  16:9    65.688 kHz  262.750 MHz (RB)
CVT:  4096x2160   23.980 Hz 256:135  52.397 kHz  223.000 MHz (RB)
CVT:  3200x2000   59.972 Hz   8:5   123.363 kHz  414.500 MHz (RB)
CVT:  3280x2000   59.991 Hz  41:25  123.401 kHz  424.500 MHz (RB)

Looks like 268.5 MHz or 424.5 MHz might be the max pixel clock.

For the 3840x1200 display, try different refresh rates until the pixel clock exceeds the max pixel clock.

mp=268.5
w=3840;h=1200
o=""
for ((r = 10;;r++)); do
	t="$(edid-decode -S --cvt w=$w,h=$h,fps=$r,rb=1)"
	p=${t// /};p=${p/*kHz/};p=${p/MHz*/}
	(( $(echo "$p <= $mp" | bc -l) )) && o=$t || break
done
echo "$o"

Result:
CVT: 3840x1200 53.970 Hz 16:5 66.438 kHz 265.750 MHz (RB)

So if the limit were 268.5 MHz, then you could try a CVT-RB timing of 3840x1200@53Hz.

 

[joevt]

Actually, HDMI timing for 3840x2160@30Hz uses 297 MHz.

So the max timing could be more like this:
CVT: 3840x1200 59.970 Hz 16:5 74.062 kHz 296.250 MHz (RB)

 

[rm-rf]

Thanks for your great replies!

From my understanding, with 3840x1200, I should be able to get up to 53Hz or even 59Hz. This should be very close to 60Hz and so I am expecting this to feel as smooth.

Does anyone of you have a direct experience with such a setup? I am really afraid it will feel sluggish ..