5-1/4' drive on modern PC

[Glen Slick]

SMSC makes a USB floppy disk controller chip.  Internally it contains
a 765 floppy disk controller controlled by an 8051 microcontroller. 
>From the datasheet it's not clear whether or not the hardware and
standard firmware support 5.25" floppy drives.

http://www.smsc.com/main/catalog/usb97cfdc2_01.html
http://www.smsc.com/main/datasheets/97cfdc2_01.pdf

Power would not have to come from the USB bus.  A USB device can have
its own power supply.