Your machine #2 video card is not powerful enough for 4k processing or proper rendering on to the display. It has to scale 4k to fit your monitors resolution.
A good CPU can compensate for inadequate GPU to an extent only. I work suggest at least a gtx970. This is also assuming you have a good monitor.
A good CPU can compensate for inadequate GPU to an extent only. I work suggest at least a gtx970. This is also assuming you have a good monitor.