Hello Katmai, thanks for joining the Intel Community.
According to the following link, the HD5500 support the following resolution https://software.intel.com/en-us/articles/quick-reference-guide-to-intel-processor-graphics
If you are not getting 4k@60Hz, please check with Thinkpad if they support that resolution.
In addition, you can send me the dxdiag report? (Start -> Run -> dxdiag -> Save All Information).
Thank you for your reply. I know that the HD5500 ought to support 4k@60Hz. I am not very confident it does so with every 4k monitor currently available, as there are two different methods to stream the picture (MST and SST) and there seems to be an issue with the SST method.
My question is: will SST ever be supported by the HD5500?
The Thinkpad officially supports that resolution & frequency, but is also unspecific about the transport method.
DxDiag.txt.zip 15.4 K
HD5500 (Broadwell) graphics does support 4K@60 in general. Setting this mode requires at least 540MHz core display clock (CDCLK) to drive a ~536MHz dot clock. If the OEM (Lenovo in this case) does not support 540MHz or higher CDCLK in the system BIOS, the system will not be able to drive 4K@60 over SST, only over MST (tiled display).
I would recommend contacting Lenovo to verify their support for SST and 540MHz CDCLK.