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AR# 67054

DDR4 IP - Extra CK/CK# clock pair generated for some 3DS RDIMMs and LRDIMMs


Version Found: v2.0

Version Resolved: See (Xilinx Answer 58435)

Targeting the following list of DDR4 3DS RDIMMs and LRDIMMs in Vivado 2016.2 and earlier generates two sets of CK/CK# clock pairs. However, their data sheets show the CK[1] pair is terminated but not used.


  • MTA18ASF2G72PDZ-2G3
  • MTA36ASF4G72PZ-2G3
  • M393A8K40B21-CTC


  • MTA36ASF4G72LZ-2G3
  • MTA36ASF2G72LZ-2G1
  • MTA72ASS4G72LZ-2G3
  • MTA72ASS4G72LZ-2G1


You can leave the extra CK/CK# clock pair connected to the 3DS RDIMM as it is terminated but not used.

Starting in Vivado 2016.2, the DDR4 IP will generate only 1 CK/CK# for the DDR4 3DS RDIMM part M393A8K40B21-CTC

Starting in Vivado 2016.3, the DDR4 IP will generate only 1 CK/CK# for the rest of the DDR4 3DS (L)RDIMMS: MTA18ASF2G72PDZ-2G3, MTA36ASF4G72PZ-2G3. MTA36ASF4G72LZ-2G3, MTA36ASF2G72LZ-2G1, MTA72ASS4G72LZ-2G3, and MTA72ASS4G72LZ-2G1
The following CRITICAL WARNING message will be seen:

Coretcl 2-1279] The upgrade of 'IP ddr4_0' has identified issues that may require user intervention. Please review the upgrade log 'ip_upgrade.log', and verify that the upgraded IP is correctly configured.

The following message is displayed in the ip_upgrade.log file:

3. Connection Warnings
Detected external port differences while upgrading 'ddr4_0'. These changes may impact your design.
-Upgraded port 'c0_ddr4_ck_c' width 1 differs from original width 2
-Upgraded port 'c0_ddr4_ck_t' width 1 differs from original width 2

These messages are safe to ignore.  Update the top level wrapper and XDC to match the port width change. 

Revision History:

04/18/2016 - Initial Release

07/05/2016 - Revised to include more parts for Vivado 2016.3

Linked Answer Records

Master Answer Records

AR# 67054
Date Created 04/18/2016
Last Updated 10/13/2016
Status Active
Type Known Issues
  • Kintex UltraScale
  • Kintex UltraScale+
  • Virtex UltraScale
  • More
  • Virtex UltraScale+
  • Zynq UltraScale+ MPSoC
  • Less
  • MIG UltraScale