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

In message BAY2-F33TWyebkWdh8B000e6fc2@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