The RPM_GRID system is used for heterogeneous RPMs in which cells in an RPM belong to different site types (such as a combination of slice, block RAM, and DSP). This is an absolute coordinate system that is mapped to a specific AMD device.
Because the cells can occupy sites of various sizes, the RPM_GRID system uses absolute RPM_GRID coordinates. The RPM_GRID values are visible in the Site Properties window of the Vivado IDE when a specific site is selected. The coordinates can also be queried with Tcl commands using the RPM_X and RPM_Y site properties.