Solving Buffer-Underrun Problems


Buffer underrun occurs when the buffer of the CD writer becomes empty. The "buffer" holds all the data before they are written to the disc. If buffer underrun happens, then the writer has no data to write. The CD-R writer can only stop writing to the disc and the mastering software will come up with an error.

Q: How to solve buffer underruns problem?

A: Buffer underruns are caused by your system not transferring data to the CD-R writer fast enough. If you are using a CD-R writer connected to a computer not purposely configured for CD-R writing, then buffer underruns can occur for a number of different reasons:


  • Fragmented hard disk. If your HDD is fragmented, data cannot be taken from it quick enough.
  • Source device is to slow. Copying "on the fly" from a slow CD-ROM, a zip drive, a floppy drive, or other slow devices is not recommended.
  • Source devices do not transfer data in a constant stream. If you have such a source device, sooner or later, it will drop behind.
  • Source devices do not sync properly. If the CD Writer starts to write before the CD-ROM or HDD has Spun up, you may get a buffer underrun straight away.
  • Slow inferfaces. Some IDE Interfaces are too slow to cope with writing "on the fly".

Any of the above hardware problems can be eliminated by creating an image of the CD before writing. You should also defragment your HDD at regular intervals, preferrable about once a week.


If you are experiencing buffer underruns but you believe your hardware is alright, then make sure all of the below are disabled.

  • Close any program that may activate on its own. This can include Screensavers, Fax and E-mail systems, anti virus software, screen savers, schedulers, and TSR software.
  • Turn off any abnormal sounds.
  • Turn off any backgrounds or animated icon which may be loaded up.

Also, before you start recording, check to see what you have running on your system. This can be done in Windows 95 and Windows 98 by pressing "Alt, Ctrl, and delete" at the same time once. You will be given a list of programs running on your system. There are only a few programs on this list which need to be running to write the CD. Close down the programs that you do not need for CD-R writing.

If you still experience buffer underruns problem after checking all the above, try the following to improve the situation:

  • Access the Performance tab of the System properties window under "system" in the control panel. Click on "File System", change the "Typical role of this computer:" to Network server. Underneath this, change the "Read-ahead optimization:" to None.
  • Then click on the CD-ROM tab, change the "Supplemental cache size:" to Small and the "Optimize access pattern for:" No read-ahead.
  • If you are still getting problems, change your "Virtual Memory" settings. By clicking on the "Virtual Memory" button you will be given a choice of either "Let Windows manage my virtual memory settings" (default) or "Let me specify my own virtual memory settings". If you change the option to the latter, you can then change your minimum and maximum settings. Depending on how much RAM you have, and what type of programs you run on your PC, your settings will change. You should set the minimum and the maximum to the same value. As a rough guide, with 64Mb of RAM and for those who uses their computer primarily for Internet exploring and word processing, the virtual memory could be set to min=max=40. If you have problems running certain programs with these settings, increase both the minimum and the maximum settings.
  • If the computer is connected to a network, you should log off the network. This is because another computer may be accessing your HDD while you are writing a CD. This may result in a Buffer Underrun.
  • Check the BIOS to disable all memory shadowing, except video and system shadowing

There is a new technology call "BurnProof" used in some recorders that aims to eliminate buffer under run problems.

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