Hard blocks are modules of code that implement certain functionality and commonly appear as PLLs and HSSI blocks on Altera devices. Though hard blocks are normally merged in a design to promote optimization and to share common physical resources, when hard blocks appear in more than one design partition in a Quartus® Prime Standard Editiondesign, they cannot be merged because optimization across partition boundaries is not allowed. In order to fully optimize hard blocks that appear in more than one design partition, the Quartus® Prime Standard Edition software auto-generates the hard_block partition during compilation and combines all hard blocks into the hard_block partition. Combining all hard blocks into the hard_block partition allows the Quartus® Prime Standard Edition software to merge and optimize hard blocks within a single partition. The auto-generated hard_block partition does not appear in the Design Partitions window and you cannot assign a post-fit netlist to the hard_block partition because the Quartus® Prime Standard Edition software recreates it during subsequent compilations. You can view a hard_block partition in the Compilation Report under Fitter in the Incremental Compilation Section report.