I just added a 2nd 4k display to my Late 2015 27inch (GPU maxed out and upgraded to 32gb ram). For some reason, it seems like my mouse when going over to the 2nd screen seems to lag just a bit to notice. Any reasons this would happen? Thanks.
Is the second display running in HiDPI mode?
(That is, "looks like 1080p")
Or, do you have it in scaled mode?
(Looks like 1440p)
If it's running in a scaled mode, I'm wondering if this isn't "putting more load" on the GPU, which might result in a bit of "lag" on the mouse's performance...?
I had it scaled, but I just put it back into native and the mouse was still lagging a bit (no difference). When I bring my mouse over to the iMac, no problem... When I bring it over to my 2nd screen, it lags... Even at native resolution.