No, those are the only two and they both work on other platforms just fine. These two are really just slightly different versions of the same driver.
You may've run across a bug exposed by running it on Irix.
That bug might be in the driver, in AOLserver, in Irix or its libraries. Without more information there's really nothing anyone can do to help you, though. "ns_pg doesn't work but ns_db does" isn't enough information ...