The High Density (HD) FPGA is an embedded FPGA built with the Skywater 130nm High Density Standard Cell library (`Sky130_fd_SC_HD <https://cs.opensource.google/skywater-pdk/skywater-pdk/+/master:libraries/sky130_fd_sc_hd/>`_).
..table:: Logic capacity of High Density (HD) FPGA IP
..[1] counted by 4-input fracturable Look-Up Tables (LUTs), each of which can operate as dual-output 3-input LUTs or single-output 4-input LUT.
..[2] bounded by the maximum speed of `GPIO cells of Skywater 130nm PDK <https://skywater-pdk.readthedocs.io/en/latest/contents/libraries/sky130_fd_io/docs/user_guide.html#design-metrics-1>`_. Higher speed may be expected when a high-speed GPIO cell is available.
..[3] I/Os are divided into two groups: GPIO and embedded I/O. See details in :ref:`io_resource`.