There is a large IBM or intel chip on the Expansion Chassis mother board. A long string of numbers on the chip indicates version/complaince.

IBM chip number ends with 352 = 2.0 compliant
Slot order = Disk i/o card in slot #4-7
DSP Farm card in any slot after disk i/o (5-7)

IBM chip number ends with 353 = 2.1 compliant
Slot order = Disk i/o card in slot #1
DSP Farm card in slot #2

*If it's an Intel chip, it's t 2.1 compliant (see above)