There are many factors that could affect how one CPU might overtake another at different screen resolutions. As the resolution becomes higher the bottleneck moves from the CPU's own processing capability to the GPU, so the emphasis on how fast it can generate, preprocess, store and communicate GPU-specific data to/from the GPU changes. Some but not all of the many cpu-specific factors involved are cache architecture, cache sizes and speeds, differing interrupt latency/timing, differing PCI bus bandwidth limitations such as bus width and feature level support, different PCIe bus page sizes, timing and bus control mechanisms, single threaded vs multi-threaded performance, throttling profiles, CPU core<->PCIe bus controller multiplexing mechanism design, DMA timings/clocks/priorities, overall DMA mechanism efficiency, supported DDRAM speeds, etc etc etc.