Intel® Quartus® Prime Pro Edition User Guide: Block-Based Design

ID 683247
Date 12/16/2019

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1.4. Design Partitioning

To use block-based design flows, you must first create design partitions from your design’s hierarchical instances. The Compiler then treats the design partitions separately to allow the block-based functionality.

The Intel® Quartus® Prime software automatically creates a top-level (|) "root_partition" for each project revision. The root partition contains all the periphery resources, and may also include core resources. When you export the root partition for reuse, the exported partition excludes all logic in reserved core partitions. To export and reuse periphery elements, you export the root partition.

When you create partitions, every hierarchy within that partition becomes part of the parent partition. Any child partitions inherit any preservation attribute of the parent. The partition creates a logical boundary that prevents merging or optimizing between partitions. The following Design Partitions in Design Hierarchy diagram illustrates design partition relationships and boundaries.

Figure 5.  Design Partitions in Design Hierarchy
  • Instances B and F are design partitions.
  • Partition B includes sub-instances D and E.
  • The root partition contains the top-level instance A and instance C, because C is unassigned to any partition.

Design partitions facilitate incremental block-based compilation and design block reuse by logically separating instances. This logical separation allows the Compiler to synthesize and optimize each partition separately from the other parts of the design. The logical separation also prevents Compiler optimizations across partition boundaries.

Block-based design requires that you plan and structure the source code and design hierarchy to ensure proper logic grouping for optimization. Implementing the correct logic grouping is easiest early in the design cycle.

Creating or removing a design partition changes the synthesis and subsequent physical implementation and quality of results. When planning the design hierarchy, be aware of the size and scope of each partition, and the possibility of different parts of the design changing during development. Separate logic that changes frequently from the fixed parts of the design.

Group design blocks in your design hierarchy so that highly-connected blocks have a shared level of design hierarchy for assignment to one partition. Structuring your design hierarchy appropriately reduces the required number of partition boundaries, and allows maximum optimization within the partition.

The Design Partition Planner (Tools > Design Partition Planner) helps you to visualize and refine a design's partitioning scheme by showing timing information, relative connectivity densities, and the physical placement of partitions. You can locate partitions in other viewers, or modify or delete partitions in the Design Partition Planner.

Figure 6. Design Partition Planner

Consider creating each design entity that represents a partition instance in a separate source file. This approach helps you correlate which partitions require recompilation, instead of reusing preserved results, when you make source code changes. As you make design changes, you can designate partitions as empty or preserved to instruct the Compiler which partitions to recompile from source code, as Design Abstraction describes.

If your design has timing-critical partitions that are changing through the design flow, or partitions exported from another project, use design floorplan assignments to constrain the placement of the affected partitions. A properly partitioned and floor-planned design enables partitions to meet top-level design requirements when you integrate the partitions with the rest of your design. Poorly planned partitions or floorplan assignments negatively impact design area utilization and performance, thereby increasing the difficulty of timing closure.

The following design partition guidelines help ensure the most effective and efficient results. Block-based design flows add steps and requirements to the design process, but can provide significant benefits in design productivity.