Pictures from ebay, anyone know what chip this is ?
At a guess, it is a "IBM-46M0864-46M0832-Feature-Key-for-Upgrading-IBM-M1015-RAID-5-50". (Google image search is great).
My guess it is a small 6-pin programmable micro that is coded in a way that it is very hard to copy. Perhaps the RAID send this board a random code, and this chip replies with a correctly hashed version of the code back. This would mean that capturing the communication is useless because it will be different every time.
If it just sends only, then if you had one, you could capture the code and try and make a circuit to copy the functionality.
It seems like it can run with two wires so power and data are sent over the same two wires. Something like the Dallas/Maxim 1-Wire technology.