Intel® Hyperflex™ Architecture High-Performance Design Handbook

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ID 683353
Date 10/04/2021
Public
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5.2.3. Fast Forward Limit

The critical chain has the limiting reason of Path Limit when there are no more Hyper-Register locations available on the critical path, and the design cannot run any faster or implement further retiming. Path Limit also indicates reaching a performance limit of the current place and route result.

The Path Info column displays the information when the critical chain is a Path Limit. This column indicates that the chain is too long. However, you can improve performance by retiming a register into the chain. If the report lists no entries for bypassed Hyper-Register in the Register column, this absence indicates that there are no Hyper-Register locations available.

Path Limit does not imply that the critical chain reaches the inherent silicon performance limit. Path Limit indicates that the current place and route result reaches a performance limit. Another compilation can result in a different placement that allows Hyper-Retiming to achieve better performance on the particular critical chain. Typically, path limit occurs when registers do not pack into dedicated input or output registers in a hard DSP or RAM block.

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