As far I know there is nothing unusual that the second card receives less speed. You are not the only one.

About the bios. It's another version. I think that the new one contains a older bios version.

You can use a atiflash to change the versions. http://www.overclock.net/t/1353325/tutorial-atiwinflash-how-to-flash-the-bios-of-your-ati-cards