Considering all Sequent I/O cards communicate I2C, you can scan the bus for attached devices and detect which cards are connected and what stack-level settings they have. One little problem here, there are a few cards (we started replacing them) that use the same IO expander chip, so you will not be able to detect the exact type of the connected card. Here is the list of the I2C addresses for all cards, including the obsolete ones.