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AM625: DDR configuration

tom zhang
Prodigy 100 points
Part Number: AM625
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi All:

     Now we want to support ISSI DDR,  and can work in -40°c - 125°c

     We write the configs at TI Sysconfig web, and check the configs with our DDR vendor.

     When we use the dtsi of this configuration on board,  CPU usage has reached 100%, the board can't work normally.

     Can you help us resolve this?

    Thank you.

  • 0
    TI__Guru* 86740 points

    Are you using DDR4 or LPDDR4?

    If you configure the dtsi for <85C, and execute at these temps do you still experience the performance degradation?

    Note that setting the operating temp >85C will increase the refresh rate 4x.  This increase in is required by the memory JEDEC specs to ensure the data contents are retained at higher temperatures.  The extra refresh commands may be pushing the total available bandwidth beyond 100%

    What CPU usage do you experience at <85C?

    Regards,

    James

  • 0 in reply to JJD
    Prodigy 100 points

    Are you using DDR4 or LPDDR4?

    - DDR4

    If you configure the dtsi for <85C, and execute at these temps do you still experience the performance degradation?

    - <85C,the cpu idle is about 22%, which meets our performance requirements.

  • 0 in reply to tom zhang
    TI__Guru* 86740 points

    Hi Tom,

    Ok, thanks for the info.  So it appears the 4x increased refresh rate is eating up the remaining 22% of idle headroom, which is why you are experiencing errors.  You will have to optimize your application to create more idle time with the <85C configuration.    

    Are you configuring for 800MHz?    Can you provide the ISSI configuration file, there may be some opportunity to optimize timing, but ultimately i think you will need to check your application implementation and see if you can improve the cpu load.

    Regards,

    James