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CD writing is a real-time process which must run constantly at the selected recording speed, without interruptions. The CD recorder's buffer is constantly filled with a reserve of data waiting to be written, so that small slowdowns or interruptions in the flow of data from the computer do not interrupt writing.
A buffer underrun error means that for some reason the flow of data from source (e.g., hard disk, CD-ROM drive) to CD recorder was interrupted long enough for the CD recorder's buffer to be emptied, and writing was halted. If this occurs during an actual write operation rather than a test, your recordable disc may be ruined.
Possible Causes of Buffer Underruns
Hard Disk
Extremely fragmented hard drive.
Not enough space in temporary directory.
Hard disk compression may cause buffer underruns. We do not recommend writing from a compressed hard disk or disk partition.
"Dumb" thermal recalibration (only on very old hard drives).
Other Hardware
Spindown of CD-ROM drives you're copying data or audio from.
Slow source devices.
Source devices that transfer data in bursts.
Incorrect recorder controller settings.
Inability of the devices to sync properly.
Overall system configuration.
Computer unable to allow fast enough data transfer.
Conflicts with old device drivers. Do not use 16-bit (real-mode) device drivers in Windows 95 or 98. REM out any old CD-ROM drives you may have in your CONFIG.SYS file. (You don't need them anyway.)
Setting hard drive read ahead optimization to "none" may cure buffer underruns in some cases. (Go to the Start menu | Settings | Control Panel | System
| Performance | Advanced Settings/File System | Hard Disk and set "Read-ahead optimization" to "None."
Networks
Recording across the network (a network may be too slow to maintain adequate throughput speed).
Files to Be Recorded
Recording many small files.
Damaged source files (data loss).
Trying to record files in use by the system or other applications.
Other
Copying from a CD that is scratched, dirty, or damaged.
Recorder malfunction.
Checks / Prevention
Defragment your hard drives at least once a week.
Do not record across a network. Copy the desired files to your local hard drive.
If your source hard disk is more than five years old, make sure it does smart thermal recalibration.
Record at a slower speed.
In any operating system, always using the newest drivers from your SCSI controller card manufacturer.
It may be necessary to write audio at slower speeds than those you can achieve for data, since writing CD-DA audio requires streaming more bits per second to the recorder.
Keep the CDs, the recorder, and your source CD-ROM drive free of dust.
Make sure your SCSI card is FULLY ASPI-compliant.
Do not try to copy empty directories, zero byte files, or files that may be in use by the system at the time of recording.
If your data includes more than 10,000 very small files, create a disc image first, or record at a slower speed.
The temporary directory should always have space free at least twice the size of the largest file you are recording.
The entire computer, from the motherboard bus to the recorder itself, needs to be configured properly for faster recording and highest maximum sync transfer rate.
Change the DMA transfer rate for the SCSI card being used.
Try a different brand of recordable disc.
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