Certain Xilinx devices use stacked silicon interconnect (SSI) technology. In these devices, the total available resources are divided over multiple super logic regions (SLRs). The connections between SLRs use super long line (SSL) routes. SSL routes incur delays costs that are typically greater than standard FPGA routing. To ensure designs operate at maximum performance, use the following guidelines:
- Register all signals that cross between SLRs at both the SLR output and SLR input.
- You do not need to register a signal if it enters or exits an SLR via an I/O buffer.
- Ensure that the logic created by Vitis HLS fits within a single SLR.
If the logic is contained within a single SLR device, Vitis HLS provides a -register_all_io option to
the config_rtl command. If the
option is enabled, all inputs and outputs are registered. If
disabled, none of the inputs or outputs are registered.