BOM is bill of materials....the parts that go into making a card, whether mobo, cpu, mem, vga...the list of SMD's and such that make up the component. Usually in revisions of a product, this changes. If it's a pcb change, then typically you get a whole new product name. This is why ASUS, gigabyte, etc have many boards that are the same, but different name, slightly different functionality. What differs between the products is the BOM(like Striker and P5N32-E, but not). this means not the main parts(at least to me), but hte supporting parts. Not memory IC's, nor gpu, but all the other parts, capacitors and such.