Thank you for contacting Intel Embedded Community.
It is unclear what is the clk issue that you are referring. The known issues related to this subject are listed in a detailed way in the errata AVR1, AVR50, and AVR54; on pages 18, 34, and 35 of the Intel(R) Atom(TM) Processor C2000 Product Family Specification Update document # 329460, also on pages 9 and 10 of this document you may find the steppings affected by these problems.
The Intel(R) Firmware Support Package POSTGOLD4 is the suggested for Intel(R) Atom(TM) Processor C2000 Product Family. You can confirm this information in the Intel(R) Firmware Support Package for Intel(R) Atom(TM) Processor C2000 Product Family for Communications Infrastructure POSTGOLD4 Release Notes document # 333408.
On the other hand, in order to help you with your firmware development process, please refer to the tools listed at the following website:
We hope that this information may help you.