Why am3354 can recognise 256MB from MT41J256M16HA-125

Eric Lam

Other Parts Discussed in Thread: AM3354

We're using am3354 with Micron MT41J256M16HA-125 on our target board. Everything seems working fine, except that the am3354 can just recognise 256MB of ram. But, the real capacity of this DDR3 should be 256Mb x 16 = 512MB. All the 16-bit data bus and A0 ~ A14 address bus are connected. What could be the reason ? I bought this DDR3 from some supplier in China. Can this DDR3 be a fake one ?

We tried the same sw using SD card to boot on a Beaglebone board I purchased from China, it can recognise 512MB ram capacity successfully. The only difference I see is that the DDR3 used on that Beaglebone board is MT41K256M16HA-125, which is a 1.35V low power DDR3. But, interestingly, the DDR3 voltage used on the Beaglebone board is 1.5V. This makes me feel very strange why the manufacturer of Beaglebone didn't use MT41J256M16HA-125 directly. Is there any hidden reason here ?

Very nervous as the progress gets stuck ...

over 11 years ago

0 Miroslav Kiradzhiyski XID over 11 years ago

TI__Mastermind 25235 points

Hi Eric,

Please try passing the correct size to your kernel boot arguments:

mem=512M

Best regards,
Miroslav

0 Biser Gatchev-XID over 11 years ago

TI__Guru**** 393215 points

Hi Eric,

Did you use the same SD card on both boards?

As for the MT41K256M16HA-125 1.35V low power DDR3, it's backward compatible with MT41J256M16HA-125 and can work at 1.5V with no problem.

0 Eric Lam over 11 years ago in reply to Miroslav Kiradzhiyski XID

Intellectual 350 points

Hi Miroslav,

But, the problem is uBoot detects it's a 256MB ram. It's still not going to the phase of booting kernel. Did you mean that I can just ignore what the uBoot detects, and add mem=512M argument to the kernel boot ?

0 Eric Lam over 11 years ago in reply to Biser Gatchev-XID

Intellectual 350 points

Yes, the same SD card is used to boot on both boards. If the MT41J256M16HA-125 that we purchased in China's vendor is not fake, I can't think of any other reason why it's so strange ???

We've ordered new MT41J256M16HA-125 from some vendor in USA. I'm just worried the same problem still exists, which may be related to the sw. That's a frustrating.

0 Biser Gatchev-XID over 11 years ago in reply to Eric Lam

TI__Guru**** 393215 points

The two memories are identical as configuration, timing parameters, etc. You will be able to localize the problem when you test with a memory from another vendor.

0 Miroslav Kiradzhiyski XID over 11 years ago in reply to Eric Lam

TI__Mastermind 25235 points

Eric Lam said:
But, the problem is uBoot detects it's a 256MB ram. It's still not going to the phase of booting kernel. Did you mean that I can just ignore what the uBoot detects, and add mem=512M argument to the kernel boot ?

Sorry, Eric, I thought the Linux kernel detected less RAM.

Have you modified any of the Physical Memory Map values inside <u-boot_dir>/configs/am335x_evm.h ?

/* Physical Memory Map */
#define CONFIG_NR_DRAM_BANKS       1       /* 1 bank of DRAM */
#define PHYS_DRAM_1           0x80000000   /* DRAM Bank #1 */
#define CONFIG_MAX_RAM_BANK_SIZE   (1024 << 20)   /* 1GB */

If you haven't, then I suggest you follow Biser's suggestion.

Best regards,
Miroslav

0 Eric Lam over 11 years ago in reply to Miroslav Kiradzhiyski XID

Intellectual 350 points

Hi Miroslav,

No, we didn't change am335x_evm.h, and I confirmed that the contents of ours are identical to yours.

Boards remounted new Micron DDR3 ram purchased from USA will be available next week. Hope my worry will be gone after getting boards.

Thanks a lot !!

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Why am3354 can recognise 256MB from MT41J256M16HA-125