Hi i need make an ISL between 2 switches DS300B ---  SilkWorm 4424, each one have a diferent FOS the 300 have v6.2.0c and 4424 have  v5.3.0_emb1, i have a couple question about this?

1.- I need to upgrade de FOs of both switches?  Is necesary  have the same FOs in 2 switches?

2.- where can i check the operatibility matrix between FOs?

thanks, in advance and regards