I am still wondering how to update firmware,I take a wide guess that maybe there should be a boot script to load the file “boot_3r4.ld” and “ip_fxs_3r4.ld”. as I had never succed in loading any of them manually.
there is a url maybe helpful:
http://www.xs4all.nl/~borkhuis/vxworks/basicNetConfiguration.txt
when you search on google by key words GW3004, you will find that there have been SIP firmware for GW3000 series already.but they all in Japanese.