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ZyXEL Prestige 660HW-67

The 660HW-67 was distributed in Germany as the "WLAN Modem 100" through the Arcor ISP. It came with the firmware QD.7 which seems to be originally made for AOL.

To get the router ready for ADSL2+, I needed the QQ.7 firmware which is the original one.

Firmware crossgrade


The big problem is that the rom-0 of the original firmware is 48 KiB whereas that of the AOL firmware is only 16 KiB. Usually, you make an upgrade by updating the rom-0 file (which contains default settings) and then update the firmware itself which then reads the new default settings upon the next boot. Since the router didn't accept the new settings, it stuck after the reboot.

This is how it works (using the serial connector on the PCB and a terminal program):

  1. upload the new firmware file completely
    • the router will complain that the rom-0 doesn't match and ask you to upload a new firmware
  2. upload the new firmware again but cancel the upload after about 600 KiB (~12 min at 9600 baud)
    • the router will boot into a debug mode
  3. upload the new rom-0 file
  4. upload the new firmware file


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