iMac Firmware Update eliminates (non-USB) floppy drive capability

The iMac (at least the Revision A and B versions) has a "hidden" floppy disk drive controller that allows you to connect an "ordinary" floppy drive (bypassing the need to use a USB floppy drive). iDrive's iFloppy is one example of a kit that works this way. Corporate Systems Center sells a similar solution.

Mark Clark found that, after installing the iMac Firmware Update, these drives will no longer work. Apparently, the update removes the needed floppy disk drivers. Mark checked with both iDrive and CSC and they confirmed this.