[U-Boot-Users] Why the contents in SDRAM stay?

Wolfgang Denk wd at denx.de
Wed Jul 14 06:25:00 CEST 2004

In message <BAY2-F33TWyebkWdh8B000e6fc2 at hotmail.com> you wrote:
> One interesting thing I found is, I used mm to change the first 4 bytes at 
> address 0, which is suppose to belong to SDRAM, to 0xdeaddead. Then I turned 
> off the power. After I turned on the power, I used md to check the memory. 
> The content at address 0 was still 0xdeaddead. I changed the value several 

That's not interesting, it's normal with good RAM chips.

> BTW, after I turn off the board I waited for long enough (1-2 minutes) to 
> turn it on.

That's not long enough. Wait a day :-)

Or check memory by running a checksum (crc32 command) over a  largaer
area  -  say  1  MB, and then try again. You will see that while most
cells keept their content, some don't.

Best regards,

Wolfgang Denk

Software Engineering:  Embedded and Realtime Systems,  Embedded Linux
Phone: (+49)-8142-4596-87  Fax: (+49)-8142-4596-88  Email: wd at denx.de
I paid too much for it, but its worth it.

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