Forum Discussion

zjj's avatar
zjj
Icon for Occasional Contributor rankOccasional Contributor
3 months ago
Solved

ram retiming

In my project with agilex7, I have added the following the setting: set_global_assignment -name ALLOW_RAM_RETIMING ON so I think quartus tool should execute the ram retiming But the fit.retimg.rpt...
Timing
  • KennyT_altera's avatar
    KennyT_altera
    3 months ago

    H Zjji, 

     

    Enabling ALLOW_RAM_RETIMING allows Quartus to retime across RAMs when the RAM implementation supports it, but it does not guarantee that every RAM/FIFO instance can be retimed. In this case, the reported node is inside the FIFO RAM hard block, so Quartus cannot move registers through that block boundary.

    To improve timing, the recommended action is to modify the RTL/IP structure by enabling optional RAM/FIFO input/output registers, or by adding pipeline registers before or after the FIFO RAM path. This is why the report suggests manual register repositioning even though RAM retiming is enabled.

     

    Thanks,

    Best regards,
    Kenny

     

KennyT_altera's avatar
KennyT_altera
Icon for Super Contributor rankSuper Contributor
3 months ago

H Zjji, 

 

Enabling ALLOW_RAM_RETIMING allows Quartus to retime across RAMs when the RAM implementation supports it, but it does not guarantee that every RAM/FIFO instance can be retimed. In this case, the reported node is inside the FIFO RAM hard block, so Quartus cannot move registers through that block boundary.

To improve timing, the recommended action is to modify the RTL/IP structure by enabling optional RAM/FIFO input/output registers, or by adding pipeline registers before or after the FIFO RAM path. This is why the report suggests manual register repositioning even though RAM retiming is enabled.

 

Thanks,

Best regards,
Kenny