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DDR3 throughput

Michael P
Expert 1810 points

SPRABK5 (revision A) describes DDR3 command latency and throughput, but claims it was running with DDR3 at 1600 MHz.  SPRZ334G says that DDR3 is limited to 1333MT/s.  How should we derate the performance described in SPRABK5 if we actually operate at 1333 MT/s rather than the rate claimed in SPRABK5?

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    TI__Mastermind 46460 points

    Michael,

    There is no simple answer to that question.  If the throughput was limited by DDR3 bandwidth, then the numbers would simply scale by 1333/1600 or 83%.  However, since the throughput varies by EDMA TC number, you can see that there are other limiting factors.  Also, these results are presented in units of time (CPU cycles).  They do not clearly separate latency from throughput.

    We recommend that you benchmark the critical portions of your application and then we can help you tune your system.  There are transfer techniques using EDMA that can load the DDR3 to its maximum bandwidth.  Of cource this is limited by many factors in your application such as which TC is used, where the data is going and block sizes.  That is why tuning your system will be more successful than us explaining these sterile throughlut numbers.

    Tom