A few things to note about Expansion Chassis!
1) PCI Host cards and Backplane Boards are made of various chipset DEC, INTEL, Pericom & Texas Instruments
listed in from oldest to newest.
2) The DEC uses a 3M Ribbon Cable that is very difficult to find but the INTEL. Pericom & TI use a VHDCI SCSI cable that is readily available.
Do NOT use a cable length more than 1 meter (3 FT) or you will have stability problems or cards not recognized.
3) For proper operation in a PowerMac G4 running OS9 you should use host & expansion cards with INTEL chipset
What happens is with the newer Pericom chipset is not all of the Expansion Slots will be recognized by OS9 & ProTools & DigiTest
Running OSX the newer Pericom chipset works fine though.
4) You can differentiate chipsets on the PCI cards by looking at the Large chip on the Board
Backplane Boards that are inside the chassis are bit tricky as the large chip is usually on the underside of the board.
I've attached a photo for reference.