An important point to clarify is the common misconception that a 64 bit device driver is needed for the PowerCore to be able to use more than 4 GB of RAM in a host program. That is not the case.
Mac OS X 10.6 boots into 32 bit mode by default and is fully capable of running a 64 bit application while the kernel is running in 32 bit mode. This gives you the advantage of being able to address more than 4 GB of RAM in a single application, and use the 64 bit instruction set while using a 32 bit device driver with the PowerCore.
A 64 bit device driver is only needed when the kernel needs to address more RAM -- for instance when using graphic cards with > 1 GB of RAM on it -- and to store increasingly large paging tables on systems with 32+ GB RAM.