Figured this one out -- crc32 a20000000 will tell you, and you can use zip/unzip on a computer to figure out the match. 

On Wed, Oct 8, 2008 at 9:11 PM, Brian Whitman <brian@echonest.com> wrote:
Hi Dave, 

Note sure. I've always used address a2000000. I also like to check the
CRC to ensure that the image loaded into memory is identical to the
one on disk.

Do you know how to check the CRC of an uploaded file via kermit to u-boot?