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Linux/AM3894: AM3894 : Memory issues(DDR2)

unseok ham
Prodigy 70 points
Part Number: AM3894

Tool/software: Linux

Hello,

I am currently using the AM389x series, and I have memory related questions.

We used 8 DDR2 (x16 / 256MB) and connected all CS0 / CS1 to use 2GB of physical memory board.
However, we recently learned that the AM389x series does not guarantee functionality for CS1.

So we are considering two ways to use the CS0 to operate the board.

The first is to use 4 DDR2 (x16 / 256MB) and connect only CS0 to use 1GB of physical memory. In this regard, I want to use 256MB for the kernel and 768MB for the user area.
I'd like to know if this is possible.

The second method is to use 8 DDR2 (x8 / 256MB) and connect only CS0 to use 2GB of physical memory like existing board.
In the second method, since the data bandwidth of DDR2 is small, we are worried about the performance degradation between CPU operations.

Best Regards,

unseok ham

  • 0
    TI__Guru**** 170625 points

    Hi unseok ham,

    unseok ham said:
    The first is to use 4 DDR2 (x16 / 256MB) and connect only CS0 to use 1GB of physical memory. In this regard, I want to use 256MB for the kernel and 768MB for the user area.
    I'd like to know if this is possible.

    This should be possible. DM816x/AM389x TI EVM (link below) comes with similar configuration, it has 1GByte DDR3 on CS0.

    For more info regarding the default 1GByte memory map and DDR config, refer to below pointers:

    Regards,
    Pavel

  • 0 in reply to Pavel Botev
    Prodigy 70 points

    Hi, Pavel

    First of all thank you for your reply to the first question.

    I have additional questions about the second option.

    The second method is to use 8 DDR2 (x8 / 256MB) and connect only CS0 to use 2GB of physical memory like existing board.

    In the second method, since the data bandwidth of DDR2 is small, we are worried about the performance degradation between CPU operations

    So, if you choose a DDR with a small data bandwidth width, you really wonder if the performance on the whole system is degraded.
    (In terms of CPU, it has the same interface with 32-bit.)

    And there is no mention of DDR with 8-bit data path in am389x datasheet. Is 8-bit ddr2 not compatible with am389x?

    (In the 9.3 data sheet, there is only an external dram with a 16-bit / 32-bit data path.)

     

    Regards,

    Unseok ham

  • 0 in reply to unseok ham
    TI__Guru**** 170625 points

    unseok ham,

    Your understanding of AM389x datasheet is correct. You can not place four x8 DDR2 chips per EMIF.

    Regards,
    Pavel