The N2800 throttles aggressively. When it gets hot (over 75°C), the GPU underclocks, causing frame drops and pixelation.
For a detailed technical report to include in support requests or system documentation, follow these steps using the Intel Graphics Command Center (Intel GCC) Open Intel GCC Ctrl + Alt + F1 intel atom n2800 graphics driver high quality
If you have an old, buggy driver, a "Clean Install" is the best way to restore quality: The N2800 throttles aggressively