Xilinx UltraScale+ devices support Dynamic Function eXchange (DFX), which provides the capability to dynamically change the configuration of a portion of the device, while the rest of the device continues to operate normally. The Vivado software tool flow lets you compile designs using an in-context methodology. The solution requires multiple passes through place and route.
The first pass establishes the static design implementation result along with the first RM for each RP. Then all subsequent place and route runs are done in context with that initial static image. A fully routed and locked static design database that contains netlist and placement and routing information for the entire static region must be loaded into Vivado before implementing any RM beyond the first.
The Abstract Shell solution reduces the requirements for this in-context flow. Because the static design is locked, it cannot (and must not) be modified when new RMs are implemented. The context is still critical, and the path through the tools does not change. However, instead of loading a full static design image, you can use an Abstract Shell checkpoint. This Abstract Shell contains only the minimal logical and physical database necessary to:
- Implement a new RM within a specific RP
- Validate timing and pass PR Verify
- Generate a partial bitstream for the RM
By using this approach, you can:
- Reduce runtime and memory usage for each RM compilation (beyond the first)
- Reduce the file size of the “static” design checkpoint for each RP
- For designs with multiple RPs, implement all RMs in parallel
- Generate partial bitstreams without the need to load the full static design
- Hide proprietary information that exists within the static design
- Avoid license checking for any IP in the static design
As a point of comparison, here is the fully routed design checkpoint for UG947 Lab 9. This tutorial design targets a Virtex UltraScale+ VU9P and has two RPs for shift and count functions. u_shift is the pblock in the lower left and u_count (selected) is above and to the right. This image is cropped to show only the top two SLRs in the device.
The Abstract Shells for these two RPs strip away the vast majority of the static logic, which for this design includes the DFX Controller IP. Note that in this design with two RPs, only the target RP pblock appears in the Abstract Shell checkpoint.
For this design, the size of the full static-only design checkpoint is 58,816KB. The checkpoint sizes for the Abstract Shells for u_shift and u_count are 1,712KB and 1,873KB, respectively. The size reduction is a function of both the size of the RP pblock and the complexity of the static design. For a simple design with small RPs in a large device, the size difference can be very large. For designs with less static logic the improvement is more modest.