RAM and CAS

[crubille]

I DON'T WANT TO OVERCLOCK ANYTHING BUT ...

Looking at my script.fex for something else, i was surprised of the RAM's parameters:
408 MHz, sdram3, CAS9. 

As i dont think such a ram exist and as i read across the forum and news from olimex, i suspect that

The RAM is DDR3 1600 that is 800 MHz, cas 9 (which is typics at this rate) and it is used at 408 MHz as A13 RAM should be set at 24*x MHz as it is the value found somewhere for the A13.

So it should be possible to run the RAM with a better CAS. 

For example 408 MHz at CAS 5, but i dont check as i think that as the A13 can't run RAM up to 480 MHz
i can test 480 MHz cas 6. 

I do it and it run just fine. 


Starting huge application are not really faster (sd access mostly), but switching virtual screen or application reaction is.

Xenomai worst case and average are slightly better.


I repeat, there is no overclocking, just using the RAM in it specified timing.

[crubille]

It look like the dram rate set in the script.fex file is not applied, but the cas is.

So using 408 MHz, and CAS 5 run fine.


I also see that the MALI run at only 180 MHz. Really, it's base clock is hard coded in the kernel but the divisor is applied. I set the divisor to 1 for the mali and now it run at 360 MHz.

[Tele]

I tested this.

if :
dram_clk = 480
dram_cas = 6
then:

Code Select Expand


root@sun5i># ramspeed -b1   
RAMspeed (GENERIC) v2.6.0 by Rhett M. Hollander and Paul V. Bolotoff, 2002-09

8Gb per pass mode

INTEGER & WRITING         1 Kb block: 1128.34 MB/s
INTEGER & WRITING         2 Kb block: 1067.21 MB/s
INTEGER & WRITING         4 Kb block: 1049.02 MB/s
INTEGER & WRITING         8 Kb block: 1044.45 MB/s
INTEGER & WRITING        16 Kb block: 1029.53 MB/s
INTEGER & WRITING        32 Kb block: 1018.56 MB/s
INTEGER & WRITING        64 Kb block: 1009.30 MB/s
INTEGER & WRITING       128 Kb block: 1007.07 MB/s
INTEGER & WRITING       256 Kb block: 1006.03 MB/s
INTEGER & WRITING       512 Kb block: 1006.03 MB/s
INTEGER & WRITING      1024 Kb block: 1006.22 MB/s
INTEGER & WRITING      2048 Kb block: 1006.67 MB/s
INTEGER & WRITING      4096 Kb block: 1006.39 MB/s
INTEGER & WRITING      8192 Kb block: 1005.57 MB/s
INTEGER & WRITING     16384 Kb block: 1003.77 MB/s
INTEGER & WRITING     32768 Kb block: 1000.44 MB/s
root@sun5i># ramspeed -b2
RAMspeed (GENERIC) v2.6.0 by Rhett M. Hollander and Paul V. Bolotoff, 2002-09

8Gb per pass mode

INTEGER & READING         1 Kb block: 3899.33 MB/s
INTEGER & READING         2 Kb block: 3923.43 MB/s
INTEGER & READING         4 Kb block: 3882.49 MB/s
INTEGER & READING         8 Kb block: 3908.51 MB/s
INTEGER & READING        16 Kb block: 3929.51 MB/s
INTEGER & READING        32 Kb block: 3921.80 MB/s
INTEGER & READING        64 Kb block: 2694.33 MB/s
INTEGER & READING       128 Kb block: 2386.05 MB/s
INTEGER & READING       256 Kb block: 1419.12 MB/s
INTEGER & READING       512 Kb block: 365.48 MB/s
INTEGER & READING      1024 Kb block: 309.78 MB/s
INTEGER & READING      2048 Kb block: 291.41 MB/s
INTEGER & READING      4096 Kb block: 283.83 MB/s
INTEGER & READING      8192 Kb block: 281.63 MB/s
INTEGER & READING     16384 Kb block: 281.58 MB/s
INTEGER & READING     32768 Kb block: 281.24 MB/s
root@sun5i>#


if :
dram_clk = 408
dram_cas = 9
then:

Code Select Expand


root@sun5i># ramspeed -b1
RAMspeed (GENERIC) v2.6.0 by Rhett M. Hollander and Paul V. Bolotoff, 2002-09

8Gb per pass mode

INTEGER & WRITING         1 Kb block: 1088.37 MB/s
INTEGER & WRITING         2 Kb block: 1065.26 MB/s
INTEGER & WRITING         4 Kb block: 1050.43 MB/s
INTEGER & WRITING         8 Kb block: 1025.78 MB/s
INTEGER & WRITING        16 Kb block: 1034.18 MB/s
INTEGER & WRITING        32 Kb block: 1020.21 MB/s
INTEGER & WRITING        64 Kb block: 1008.08 MB/s
INTEGER & WRITING       128 Kb block: 1005.37 MB/s
INTEGER & WRITING       256 Kb block: 1007.20 MB/s
INTEGER & WRITING       512 Kb block: 1006.96 MB/s
INTEGER & WRITING      1024 Kb block: 1006.65 MB/s
INTEGER & WRITING      2048 Kb block: 1006.91 MB/s
INTEGER & WRITING      4096 Kb block: 1006.65 MB/s
INTEGER & WRITING      8192 Kb block: 1006.16 MB/s
INTEGER & WRITING     16384 Kb block: 1004.27 MB/s
INTEGER & WRITING     32768 Kb block: 1000.45 MB/s
root@sun5i># ramspeed -b2
RAMspeed (GENERIC) v2.6.0 by Rhett M. Hollander and Paul V. Bolotoff, 2002-09

8Gb per pass mode

INTEGER & READING         1 Kb block: 3900.38 MB/s
INTEGER & READING         2 Kb block: 3925.16 MB/s
INTEGER & READING         4 Kb block: 3882.90 MB/s
INTEGER & READING         8 Kb block: 3915.62 MB/s
INTEGER & READING        16 Kb block: 3923.93 MB/s
INTEGER & READING        32 Kb block: 3922.36 MB/s
INTEGER & READING        64 Kb block: 2702.79 MB/s
INTEGER & READING       128 Kb block: 2193.79 MB/s
INTEGER & READING       256 Kb block: 1419.18 MB/s
INTEGER & READING       512 Kb block: 365.61 MB/s
INTEGER & READING      1024 Kb block: 309.75 MB/s
INTEGER & READING      2048 Kb block: 291.87 MB/s
INTEGER & READING      4096 Kb block: 283.86 MB/s
INTEGER & READING      8192 Kb block: 281.85 MB/s
INTEGER & READING     16384 Kb block: 281.54 MB/s
INTEGER & READING     32768 Kb block: 281.65 MB/s
root@sun5i>#


I cannot see any relevant difference.
What did I miss ?

[crubille]

It should be set in the u-boot code  - These parameters are not applied from the .fex