Unusable display on Ubuntu with S2600WTT

Hello Gents,

We're experiencing strange problems with various Ubuntu versions on a S2600WTT server (using a Xeon E5-2660 v4):

Using the onboard graphics, the display is excessively slow, at a point it is barely usable.

Additionally, we're experiencing a slow memory throughput. Both problems might be linked. Updating the BIOS and playing with almost all settings there didn't change the problem.

Any clues on what might cause that?

Thanks for your input.