What is TD64 ?
TD64 (Track Disk 64) is a new device driver standard for accessing disks larger than 4GB. It is supported by some of the latest boards from Phase5 and others.
As of 4.2 PFS-2 has support for this standard which is used when accessing data past the 4GB limit of the standard trackdisk type devices.
If the card controlling your disks does not support the TD64 standard you should use the direct SCSI version of PFS-2.
Note that NSDPatch, available on AmiNet, allows some older device drivers to emulate the new standard. This patch should be applied before PFS-2 uses the TD64 protocol. This means that your boot partition cannot use it !