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why program run in sdram very slow

ron chow
Prodigy 240 points

My program run in sdram of RM48HDK, the EMIF_CLK is 100MHz, i test the run speed,the same program run in flash inside chip ,the time is 140ms,but spend 1.4s in sdram.

4606.950_sdramRunSpeed_test.zip

in this ZIP file,there are 2 CCS project, the 950_bootloader project have generate a bin ,burn address start at 0x0. the app_project have generate a bin also,burn address start at 0x180000.you can try and test,and please answer my question,thanks very much

  • 0
    TI__Guru 68920 points

    Ron,

    This is normal because the RM48 doesn't include an instruction cache.   Thus each instruction fetch pays a latency penalty to get to SDRAM.     Also I should note that the RM48 spec doesn't support 100MHz on SDRAM, so please be aware of this.  The actual speed is something more like 55MHz.  

    SDRAM on the RM48 is useful mostly for large buffers, ex. for the EMAC or the USB ports.  The device has 3MBytes of on chip memory and you should try to fit your code into this memory if at all possible.

    Someday we might have an RMxx part with Instruction and Data Cache, so please keep your eye out if that's what you need.