The following table provides a guideline for the recommended number of control sets, depending on the target device size.
| Guideline | Percentage of Control Sets |
|---|---|
| Acceptable | Less than 7.5% of the total number of control sets in the device |
| Reduction Recommended | Between 7.5% and 15% of the total number of control sets in the device |
| Reduction Required | Greater than 15% of the total number of control sets in the device |
These guidelines assume the following:
- Typical control set capacity: 1 per 8 CLB registers
- Total number of control sets in a device: CLB registers / 8
Determine the number of control sets in a design using
report_control_sets -verbose.
Tip: The
number of unique control sets can be a problem in a small portion of the design,
resulting in longer net delays or congestion in the corresponding device area.
Identifying the high local density of unique control sets requires detailed
placement analysis in the Vivado IDE
Device window, which
includes highlighted control signals in different colors.