Which Adaptec scsi cards work on a g4 PowerMac?

When it comes to SCSI cards that are compatible with a G4 Power Mac (especially models like the Power Mac G4 AGP, Digital Audio, Quicksilver, or MDD), your best bet is to stick with Adaptec PCI SCSI cards that have native Mac OS 9 and early Mac OS X support. AFAIK, the Adaptec 2906, 2940U, and 2940UW are some of the most commonly used and supported models in this context.

One word of caution: Adaptec dropped support for Mac OS X after around version 10.3.x. So, if you're running anything newer on your G4 (like Leopard via unsupported methods), you’ll need to either rely on third-party drivers or switch to a different solution, like an ATTO SCSI card, which had better long-term Mac support.

Sorry, but I wouldn't know off-hand as I don't have the hardware to verify this. I suggest that you contact the card's supplier to find out.