[U-Boot-Users] why "go 0x0" and "go 0x0c000000" could start u-boot?

hello, everyone:

(Will somebody write to me to tell me how i can see your replies?)

when reset cpu or power up, u-boot starts, press any key to stop it automaticly boot the kernel, i test "go 0x0" and "go 0x0c000000", but two of them could go to restart u-boot! I am sure u-boot was flashed in 0x0c000000, but why "go 0x0" has the same effect?!

With my mxlads board, I know another truth, when power up, cpu exec the first cmd in 0x0c000000. (this could be set by switches)

Somebody know why?

HoHo_Zhao