The SPI-4.2 Core v7.0 provides two clocking options: Global Clock and Regional Clock. When regional clocking is chosen, the core uses regional clock buffer resources.
When implementation is run for a design with "Regional Clocking" on an XC4VLX25-FF668 device, the place-and-route tool (PAR) reports following placement error:
"WARNING:Place:119 - Unable to find location. SLICEL component ---
The AREA group contains 896 possible sites for this component. 0 of these sites were available to place this component into.
ERROR:Place:120 - There were not enough sites to place all selected components."
This issue is caused by the place and router of the ISE software.
Please install ISE6.3i Service Pack 2.