32-Bit Transfer Mode
Enabling this setting allows for 32-bit data transfers between the processor and the PCI bus. Actual transfers to the disk are always done 16 bits at a time, but enabling this option will cause a small performance improvement on the transfer from the bus to the processor.
If your disk supports this, enable it for a performance increase. Disable it if you encounter any difficulty or if your disk doesn't support it.
Note: This setting has nothing to do with Windows 3.x's "32-bit disk access" or "32-bit file access", which refer to something different entirely.