unable to move farther with compiled U-boot on Beagleboneblack

We compiled u-boot code for arm board (Beagle bone black), and try to run it from "RAM". But we are are facing problem while running it. We try to load the u-boot.bin image by giving the command "tftp 0x80800000 u-boot.bin", but it is not working after the above command we could see it was loading the file. after that we gave "go 0x80800000" command to start the execution from that address but board is proceeded with default image which is available on board.

compiled the u-boot code by giving the below commands

make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- bb.org_defconfig make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- -j4 make ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- uImage dtbs LOADADDR=0x80008000 -j4

Please let us know where we are doing wrong if any, Ans refer proper materiel to proceed farther Thanks