Compute shell leaves vNOC memory ingress unpinned (empty CONFIG.PHYSICAL_LOC), anchoring user memory off-die from HBM — costs ~20 MHz

[tinebp]

Environment: Alveo V80 (XCV80), SLASH compute shell, Vivado/Vitis 2025.2, v80-smi / VRT from /opt/xilinx/slash, Ubuntu 24.04.

Costs ~20 MHz on every user design, silently, with no diagnosable symptom from inside a reconfigurable module.

Observation

In linker/slashkit/resources/base/compute/scripts/slash_base.tcl, all eight hbm_vnoc_* NoC ingress units — which carry MEM_TAG to HBM via HBM_VNOC_INI_00..07 — are created with an empty physical location:

set_property -dict [ list \
   CONFIG.PHYSICAL_LOC {} \
   CONFIG.CONNECTIONS {M00_INI {read_bw {500} write_bw {500}}} \
   CONFIG.CATEGORY {pl} \
 ] [get_bd_intf_pins /hbm_vnoc_00/S00_AXI]