Recovering from a bad firmware

At this very moment the only way to fix bricked DSM-G600 is to use a serial console.

1. Install a serial console.
2. Now you should see which part of your firmware is failing.

   U-Boot 0.2.0 (May 11 2005 - 18:56:16)
   
   CPU:   MPC8245 V1.2 at 170.503 MHz:
   Board: Sandpoint 8245
   DRAM:  32 MB
   FLASH: FUJI_DL323BE
   In:    serial
   Out:   serial
   Err:   serial
   Hit any key to stop autoboot:  0
   ## Booting image at fff10000 ...
      Image Name:   Linux-2.4.21-pre4
      Image Type:   PowerPC Linux Kernel Image (gzip compressed)
      Data Size:    853695 Bytes = 833.7 kB
      Load Address: 00000000
      Entry Point:  00000000
    Verifying Checksum ... OK
      Uncompressing Kernel Image ... OK
   ## Loading RAMDisk Image at ffc20000 ...
      Image Name:   default
      Image Type:   PowerPC Linux RAMDisk Image (gzip compressed)
      Data Size:    3072965 Bytes =  2.9 MB
      Load Address: 00000000
      Entry Point:  00000000
      Verifying Checksum ... Bad Data CRC
   *

   Here we have a failing ram disk image.

3. Get firmware you want to flash. I suggest you to use D-Link original unmodified firmware!
4. Get program to unpack firmware image. It is located in this archive in fwbuild-0.x.tgz file. Use fwdump firmware-image. Now you have 3 files: firmware.sec1 which is u-boot formated kernel image, firmware.sec2 is u-boot formated ram disk image and firmware.sec3 you do not need.
5. And finally here is a how to upload a needed or failing image using a serial console.