• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 101 subscribers
  • Views 602 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

How to compute the edma3 transfer speed in theory

cz h
Intellectual 750 points
Other Parts Discussed in Thread: TMS320C6455

Hello, I want to compare the actual speed of the edma3 and it's theory value, my platform is based on tms320c6455,

the core frequence is 1GHz, and I use edma3 transfer data from DDR2 to DDR2, I found that the edma3 clock is sys_clk2, whose frequence is

fixed at CPU/3,so it's clock peorid is 3ns, and DDR2's clock is 250MHz, but DDR2 can transfer data on both edge of the clock ,so it's actual frequence is 500MHz

, so ,I thougnt that the speed is limited by the edma3 clock,but I'm not sure the bus width of edma3,I think it is also related with SCR, and I confused , how can I compute the transfer speed of edma3,can someone help me.

  • 0
    TI__Guru* 84110 points
    Cz,

    You said you use EDMA3 to transfer data from DDR2 to DDR2. When a transfer is running, does the DDR2 data bus stay busy with bursts or does it stop from time-to-time? How long are the bursts continuous?

    How long is your transfer? Make it as long as possible, with ACNT=64, BCNT=1000, BIDX=64. How do the bursts look on a scope?

    Try the transfer again going from DDR2 to L2. What do you observe differently about the bursting and continuity of the DDR2 bus transactions?

    Then try it from L2 to DDR2 and observe it again.

    Setup 4 simultaneous transfers, one on each Transfer Controller. Run them all starting at the same time. Observe the bus behavior and the average time to complete the operations.

    How do all of these compare?

    The DBS is another factor that comes into play, in addition to all of the parameters you talked about.

    There are too many parameters to try to make an accurate determination of theoretical speeds. You can calculate the theoretical speeds on all of the internal buses if you have the clock rate and width of those buses. That is available from Figure 4-1 in the System Interconnect section of the Datasheet.

    Regards,
    RandyP