zImage works, but not vmlinux

[f. achkar]

Hi,
I have tried to send this message some part of it was ignored, resending
sorry ...

greetings,
I'm newbie to arm linux, so pls if my issue is already addressed just
point me to that reference. I'm trying to learn, but couldn't pass the
following stage:
I have a s3c245 based board, I have a working compressed kernel image
zImage, this image boots properly via u-boot-1.1.6, however I simply
failed to load (i.e., boot vmlinux) via u-boot directly from SDRAM.

more details:

   1. I let the target boot until the message of "  Hit any key to stop
      autoboot: " for which I hit enter, (this initialized the board
      enables MMU, I-Cache, .. etc);
   2. board info as seen by u-boot
      # bdinfo
      arch_number = 0x00000648
      env_t       = 0x00000000
      boot_params = 0x30000100
      DRAM bank   = 0x00000000
      -> start    = 0x30000000
      -> size     = 0x04000000
      DRAM bank   = 0x00000001
      -> start    = 0x38000000
      -> size     = 0x04000000
      ethaddr     = ...:5B
      ip_addr     = ...200
      baudrate    = 115200 bps
   3. laod vmlinux to SDRAM :
      tftp 30008000 vmlinux
      TFTP from server ...210; our IP address is ...200
      Filename 'vmlinux'.
      Load address: 0x30008000
      Loading: T ############ .....
   4. # bootm 30008000
      ## Booting image at 30008000 ...
      Boot with Image
      do not support this address : 30008000

      Starting kernel ...

and nothing happens it probably crashed somewhere, why zImage works
while vmlinux does not?
thanks,
ferar