Unfortunately, I think Slinky is correct on this one.
If this is indeed an Apple OEM version of the ATTO card, we don't support it. The OEM versions typically use non-standard firmware that -- as you've found out -- inhibits us from controlling some of the vital parameters of the card. (This also held true for us with the OEM versions of Adaptec cards that shipped with the Blue and White G3s.)
I was hoping we might be able to do a few tricks that might make it useable, but I'm afraid I don't have anything else up my sleeve.
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--Steve Rosenthal, Digidesign ETS