Yamaha CRW3200IX Series Owner's Manual page 48

Technical Notes
CD-MRW (CD Mount Rainier ReWriting)
This method is a new standard of packet writing for a CD-RW disc and supports
defect control by the drive, background formatting, and disc ejecting during
formatting. It enables you to use a CD-RW disc like a floppy disk.
Note
Formatting a CD-RW disc using CD-MRW reduces its storage capacity by about 150 MB
since CD-MRW itself requires exclusive disc space.
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