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Performance DDR2 vs DDr3 with DM814x

Michi Yamamoto
Intellectual 610 points

Hi,

Our customer is comparing the access speed of DDR2/DDR3 with DM814x EVM.

The below is the results of the performance.

\\\\\ Test results\\\\
  Time for 1Mbytes data transfer
| Memory type          |   cycle number  |  time(msec)  |
|   DDR2   EVM        |    4993537         |    10.0             |
|   DDR3   EVM        |    5452481         |    10.9             |

-test conditon-

> The measurement was done for between < DSP - DDR>

> Cache was enabled

> GEL (included in PSP) modified :

                 DDR 333Mhz -> 400Mhz

                DMM interleave enabled

 

As you see the above results, DDR3 is slower than DDR2. It is approximately 10% .

I think Both of DDR2/DDR3 EVM have same performance if there are same memory clock, L3 bus speed and CPU speed.

My questions are :

1) The setting of memory latency for DDR2 EVM/DDR3 EVM seems to be different. The test of results is caused this matter?

Or are there other factor for performance down?

2) Generally speaking, clock speed of DDR3 is higher than DDR2's it. And DDR3's latency is longer than DDR2. In case of

memory using EVM, if  I use lower clock than spec., is it possible that the value of latency is smaller?   

 

Thank you for your help.

Michi

 

 

 

 

  • 0
    TI__Genius 15310 points

    Michi,

    At a given frequency, DDR2 will have better bandwidth (data rate) over DDR3, as DDR2 can work at low CAS latencies.

    In terms of power DDR3 will have advantage over DDR2 (1.5V Vs 1.8V)

    BR,

    Viet

  • 0 in reply to Viet Dinh
    Expert 1850 points

    Viet Dinh said:
    At a given frequency, DDR2 will have better bandwidth (data rate) over DDR3, as DDR2 can work at low CAS latencies.
    In terms of power DDR3 will have advantage over DDR2 (1.5V Vs 1.8V)

    Viet,

    Can you do similar compare with LPDDR-400?

    Thanks,

    Patrick

  • 0 in reply to patrick nefos
    TI__Genius 15310 points

    Hi Patrick,

    In Cent LPDDR1 can run max at 200MHz. DDR2 can also run at 200MHz(only selected parts). However NONE of the DDR3 devices can run at 200MHz. So a performance comparison of LPDDR1 with DDR3 is meaningless. On the other hand LPDDR1 will have slightly better throughput compared to DDR2 at 200MHz. LPDDR1 can work at even lower CL and WL compared to DDR2. Please note that in a system context, the performance improvement will be very minimal (in order of 1 or 2% max). The criteria to select between DDR2 and LPDDR1 should not be data bandwidth but power. LPDDR1 has features like partial array self refresh (PASR) etc which can save power up to 75% compared to a DDR2 device which does not support PASR.

     BR,

    Viet

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