I was checking out the BIOS files for the XFX4870X2 and could only find the master BIOS in the collection. I tried to upload the slave BIOS via GPUZ but it gave a message that it has already been uploaded. So I am not sure if you do not have it or it is just not showing.
Anyway I have uploaded it here for you if you want it.
the master BIOS (which you have) MD5 Hash: 271cb09b5964b38d41ef6db7ab46e60e
the slave BIOS MD5 Hash: 2802F887879264A50F4FCF660C638056
Anyway I have uploaded it here for you if you want it.
the master BIOS (which you have) MD5 Hash: 271cb09b5964b38d41ef6db7ab46e60e
the slave BIOS MD5 Hash: 2802F887879264A50F4FCF660C638056