An external floppy disk drive (PCGA-UFD5, PCVA-UFD1) is 3-mode compliant regardless of the supplied or optional one.
3-mode compliant means that you can read, write and format with 1.44MB/720KB, and can read and write with 1.2MB format floppy disk.
You cannot execute FORMAT, SYS, DRVSPACE, and DISKCOPY command.
An internal floppy disk drive that comes with Windows Me or Windows 2000 pre-installed model is only 2-mode compliant.
All of the 2Q models (PCG-Z505FA, PCG-F660, PCG-XE7, PCG-SR9G) is 3-mode compliant.
And about 3Q models, refer to the following,
2-mode compliant: PCG-F670, PCG-XE17, PCG-FX770, PCG-FX800, PCG-FX880K, PCGA-DSM5, PCGA-DSD5
3-mode compliant: PCG-Z505GA, PCG-C1VM, PCG-C1VG, PCG-SR19G, PCV-LX100