In the past, anyone who used a CD writer sometimes made coasters, the common term for a ruined CD-R blank. Although packet writing and UDF effectively eliminated coasters, packet-writing software was useless for batch-mode tasks, such as duplicating CDs. Those tasks demanded premastering software, which unfortunately was by no means immune to generating coasters.
Originally, CD premastering was inherently an isochronous (time-dependent) process because data had to be delivered to the write head in a continuous stream from the time the write began until it completed. If that stream was interrupted long enough for the data stored in the writer's buffer to be exhausted?an accident called a buffer underrun?the blank was ruined. Buffer underruns were particularly common with IDE/ATAPI CD writers, although they were by no means rare even on SCSI burners.
Sanyo effectively made buffer underruns a thing of the past by developing a technology called BURN-Proof (Buffer UnderRuN-Proof) and licensing it to CD writer makers. In simple terms, BURN-Proof turns off the writing LASER when it runs out of data to write (duh), and then, when data is again available, restarts the burn exactly where it left off. In effect, BURN-Proof converts CD writing from an isochronous process to an asynchronous one.
BURN-Proof works by constantly monitoring the status of the CD writer's buffer to detect a potential buffer underrun condition. If the amount of buffered data falls to a critically low level, the BURN-Proof firmware finishes writing the current sector and then turns off the writing LASER until the amount of buffered data returns to an acceptably high level. When that occurs, the BURN-Proof firmware repositions the writing LASER to begin writing where it left off.
Our first experience with BURN-Proof was with the superb Plextor PlexWriter 12/10/32A IDE CD writer. With standard IDE CD writers we hesitated even to move the mouse while burning. We walked softly and worried about vibration from passing trucks. But the Plextor 12/10/32A and later PlexWriters eliminated those worries. Plextor CD writers with BURN-Proof are so robust that we successfully burned a disc from an image file on the hard drive while we were defragging that hard drive?a guaranteed way to ruin a disc with any CD writer that lacks buffer underrun protection.
The success of PlexWriter drives with BURN-Proof made buffer underrun protection a must-have feature, so other manufacturers soon followed with similar technologies. Nowadays, even inexpensive CD writers have some form of buffer underrun protection, whether the original BURN-Proof or a competing technology. Yamaha, for example, calls its method SAFEBURN. Sony calls it Power Burn, and LITE-ON calls it Buffer Underrun Free. The various technologies differ in minor respects, but all of them work.
It takes much longer to write a disc if the buffer underrun protection kicks in repeatedly, but the write does complete normally, and we have never had a problem reading the resulting discs. Unfortunately, buffer underrun protection cannot be retrofitted to an existing CD writer. If you want buffer underrun protection (and you should), the only way to get it is to buy a CD writer that supports it. Fortunately, CD writers are very inexpensive, and if your current writer is old enough to lack buffer underrun protection you probably need a new, faster writer anyway.