Most modern CD/DVD writers implement some form of buffer-underrun protection. A
buffer-underrun occurs when the writer's buffer (high speed memory built into the writer itself
for organizing data prior to writing it onto the disk) become empty of data
before the writing process is complete. This leaves the new CD spinning in the
drive while no data is available to be written to it, resulting in
the writer essentially 'losing its place' on the disk and creating a
buffer-underrun can occur if the computer's resources are being taken up by
For example, significant use
of the hard drive that is sending data to the writer by another program can
break up the data stream going to the writer's buffer, resulting in an underrun.
This potential problem was the reason that most early CD-burners recommended
doing little else with your system while a CD was being created.
manufacturers have patented their own methods of avoiding this problem,
technology being one example, but most work in a similar way: The drive,
assisted by the burning software, monitors the amount of data in the buffer. If
this falls below a certain level, and the CD is not yet complete, the drive
suspends the writing process while taking a note of the area on the CD it was
Once a sufficient amount of
data has accumulated in the buffer again, writing is resumed from a point very
close to where it was originally halted. This effectively eliminates the problem
of buffer underrun, though running intensive applications such as games while
you are creating CDs is still not a good idea.
CD-RW disks are written using the UDF file system,
or 'packet writing' where individual sectors are written to the disk and
referenced by a single, updated address table. This has the advantage, in current versions
of UDF, of allowing individual sectors on the disk to be erased and rewritten.
Obviously, as the ability to be erased and
written over is the main advantage of CD-RW disks, this is an important feature.
is considerably more flexible than the ISO 9660 file system, removing the need for
a finite session to be created each time data is added, making the media a
lot more like a traditional hard disk. Physically, CD-RW media is different from
CD-R media, but the specifications in terms of maximum rated write speed
work the same way.
disks will generally not play in standard audio CD players, unless specified, due to the lower
reflectivity of the disks as compared to CD-ROMs or CD-R disks, and may not play
in older CD-ROM drives as they often do not support the multiread specification,
which essentially provides the ability to read less reflective media through the
use of higher amplification.
The disadvantage of the UDF
file system is compatibility. Most modern operating systems including Windows XP
still do not read all UDF formatted disks. WindowsXP will read UDF disks burned by
certain software, but not others.... To rectify this, you may need a UDF reader
program, which will be included with the software if required. Many programs
capable of burning UDF CD-RWs will include the reading software automatically on
each CD created, so it can be installed when the disk is inserted.
CD-RW disks must be formatted
with the UDF file system before they can be used, and this can be a time
consuming process, usually between 20 and 40 minutes, depending on the speed of
the CD-RW drive. Once this is done, the files can be dragged and dropped
directly to the CD drive using the standard Windows interface.
several popular UDF CD-creation programs, most coming as companion software to
traditional CD-burning software, Such as Direct-CD or Drag-To-Disk with Roxio's Easy CD Creator, or InCD with Nero. The websites for these companies also contain
comprehensive information for formatting and using CD-RW media.