Philips 65100 manual About Buffer Under RUN BUR

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ABOUT BUFFER UNDER RUN (BUR)

Buffer under run can occur when the users’ PC or a host PC cannot supply a steady and uninterrupted flow of data from the data source, typically a CD ROM or HDD, to the internal DRAM buffer of the CD writer (writer buffer) (Fig. 1). If this transfer of data to the drive writer buffer is interrupted, then the buffer is not kept full (Fig. 2). If the interuption is long enough, the "writer buffer" gets empty, the writing process stops and the disc is ruined (Fig. 3). Buffer under run occurs most frequently when users are writing to a CD-R or CD-RW disc in either Track-at-Once (TAO) or Disc-at-Once (DAO) mode.

The causes of BUR have been numerous and are related to the PC system, the system configuration or set up, and the CD writer itself. Most sources of BUR have been reduced in newer PC systems (with faster CPUs and HDDs with transparent Thermal Recalibration), and by improvements in both

CD writer and the application software.

Fig. 1, Typical CD writing process: The data that needs to be written on the disc is transferred from the source over the system bus, and is put into the DRAM buffer of the CD writer. From this buffer, the data is put onto a disc in the writing process.

CD writer

Internal DRAM buffer,“writer buffer” compensates for short interruptions in the data stream

Fig. 2, Typical CD writing process: Short interruptions in the transfer of the data over the IDE bus will cause the writer buffer level to drop.

CD writer

If the data stream is interrupted, the speed at which the data is sent to the writer is lower than the speed at which the data is written to the CD

=> the level of the writer buffer will drop.

After the interruption, the writer buffer level will rise again