Do you get corrupt data and buffer underruns when copying files to CD roms , if so maybe I can help - read on!

Like most people using CD writers I have suffered from these problems and discovered great difficulty in finding information on suitable fixes. However, after spending hours trawling around the net I have gathered together information, mainly from Mitsumi and Philips (most other CD writer manufacturers seem very shy of producing information on these problems) on hardware and system fixes that overcome the problem. From the information it is quite clear that successful CD writing is not just click and wait as the software would have us believe, but requires quite extensive system and in some cases hardware re-configuration.

To give you some idea of the extensive system and hardware re configuration that is advised for successful audio and data copying I list below my findings. I have implemented all the recommendations shown and can report that buffer underruns and corrupt data are now a thing of the past, even if it does mean that audio writing at x1 speed can be very slow, especially if file sizes are 300 to 400Mbs, typical for my recordings from reel to reel tape!

Buffer underruns are indicated when you get an error message similar to:

Write Blocks failed. Write fail. Invalid field in CDM, Block xxxxxx

CD writing is a real time process which must run constantly at the selected recording speed without any interruptions. Data must be able to be passed across the BUS from HDD to recorder without any interruption and with some mother boards this requires the BUS to have the correct BUS drivers installed. (see 5 below). The CD's recording buffer MUST be constantly filled with a reserve of data waiting to be written, if there is any hesitation during the process Buffer Underruns occur. Incidently it has been shown that increasing the hardware buffer to 2Mbs, as some manufacturers do, does not substantially reduce the possibility of underruns, the problem arises else where, slow data transfer across the BUS, too fast a recording speed when copying large files and processor interruptions during writing being the main cause. To overcome any buffer underrun problem and ensure continuous fast data transfer the following should be implemented.

It is quite clear from the information that follows that a PC dedicated to CD writing is the ideal situation - one in which all device drivers are correct, there is no requirement for auto and config files and a dedicated HDD is installed. However this is not practicle with home multi purpose PC's and so 'fixes' have to be employed. On my machine I have implemented all the 'fixes' shown below and they in no way reduce the performance of the machine or show any problems with any of my software programs - now to business!

First ensure that you have the correct and latest CD rom writer software driver installed for the copying application you use. The latest drivers are available on the Internet for CeQuadrat, Adaptec etc., choose the correct driver for your particular CD rom writer and install it before you start. Updates and bug fixes can also be found on these sites for their applications, check these out, download and install if available. Also visit your CD writer manufacturers web site ,they usually have the latest drivers for most writer applications that are approved for use with their hardware. This in fact can be quite revealing, not all writer applications are completely compatible with all hardware models even though sometimes the application is supplied free with the hardware - beware!

1: Select a partition and reserve it for the exclusive use of CD writing. Ensure you have a maximum sector size on this partition no greater than 16Kb. This means the partition should not be more than 1Ghb - to ensure 16Kb I suggest your partition should be 900Mhb or smaller, but not too small, see 2 below. Make a directory called 'temp' on this partition, this will be used during the writing process to accomodate the 'image file'. It is most important that this directory is always empty before you start a copying session and the copying partition should always be 'defragmented' before you start a copying session even though there are no files in the 'temp' directory.

If you have not heard of the recording 'temp' directory be aware that when recording, all the data is first processed into a temporary file called an 'image file' and written to the HDD. This image file is written to the 'temp' directory located on the partition chosen for CD writing. All recording software has a configuration facility enableing you to choose a partition and make a 'temp' directory. To find out how to do this with your particular software see your handbook.

2: Your HDD partition with the 'temp' directory should not be less than 2.25 times the total file size or sizes you are copying to the CD.

3: Remove or shut down all TSR (terminate and stay resident software) ie Screen Saver, System sounds, Anti-Virus, Schedulers, Fax drivers, etc. etc.. Close any program that may activate on its own. Note: Any active Screen saver MUST be shut down, any processor activity during CD copying not connected with the operation of the CD recording system will corrupt data copy and make the CD unusable - even previously accessible data will not be accessible.

If active, enter the BIOS and disable Power Management.

During the writing process do not touch the computer, in no way use the keyboard or mouse! Make sure the screensaver is switched off. CD writing and multi-tasking do not make good bed fellows!

4: Remove your config.sys and autoexec.bat files ( copy them to a floppy) and reboot your machine. If you have a clean machine 95/98 should reboot OK. How do you know if you have a 'clean' machine? - well before removing these files run Control Panel/System and choose the tab 'Device Manager' and look to see if there are any devices with a yellow ? mark against them. If so this means Windows is using a temporary driver and you should obtain the device manufacturers Windows 95/98 latest device driver and install this to remove the yellow ?. This is essential for CD drive device drivers, if you see a yellow ? against 'CD rom drives' you must obtain the correct 95/98 CD rom device driver from the CD rom manufacturer and install it.

5: Sometimes mother boards are supplied with IDE I/0 bus master drivers on a floppy or CD. If you have one of these the I/0 bus drivers should be installed, failure to do this will inhibit the working of the IDE I/0 ports and cause them to transfer data at a much slower speed than the are designed for. (slow data transfer across the BUS is the major cause of buffer underruns)

6:: Before starting a recording session always defragment the recording partition on your HDD and close ALL applications that may be running, you cannot multi task when making CD's!

7: The CD recorder MUST be set as the master on the secondary IDE port. It must NOT be on the same IDE port as the HDD.

8: The PIO mode of the recorder must be set at 3 - do not set the port at 'auto' To check and set this you must enter the BIOS and look for the PIO settings of your primary and secondary IDE ports.

Buffer underruns can be caused by 95/98 configuration errors and the following should be checked and altered if necessary.

NOTE: For the following settings to work must have more than 16Mhb of main memory.

9: Disable Auto Insert Notification: To do this right click on My Computer and select Properties and click Device Manager tab and select the CD Rom icon. Then click the Properties button and then the Settings tab and deselect 'Auto Insert Notification' then restart the system when prompted.

10: Change your HDD to a Network System. This re-prioritizes the HDD so that it is given priority over other hardware and software. Incidently, this makes your computer transfer data more quickly when using 95/98.

To do this right click on My Computer select Properties and then the Performance tab and click on the File System button and choose the Hard Disk tab. Then change the 'Typical role of this machine' - it probably shows 'Desktop Computer' - to read 'Network Server'.

Note: Before you implement 11 below you should be aware that altering 'Virtual memory' can cause the computer to crash, it is unlikely but it can happen. If you do not feel happy about this, do not implement this section!

11: Enter Control Panel and choose the 'Display' icon and look under the Settings tab and see what BIT colour you are using - it will be either 8 bit, 16 bit, 24 bit or 32 bit - make a note of this and close Display. Then right click on My Computer and select Properties and choose the Performance tab. Click on the Virtual memory button and click on 'Let me choose my own Virtual memory settings' and set the max and min as follows:

8 bit colour: select 16Mbs for both min and max.

16 bit colour: select 16Mbs for both min and max

24 bit colour: select 32Mbs for both min and max

32 bit colour: select 32 Mbs for both min and max.

Then close down and restart your computer.

12: A hot tip! From a reliable data transfer point of view you should always record at the slowest speed - x2 for data and x1 for audio - even though you may have a fancy x4 recorder. To record x4 reliably you need a very fast computer (350Mbs+) with optimised HDD to recorder BUS data transfer preferably using Ultra DMA/33 mode. Also if you must record at speeds faster than x2 you should use special CD disks that have been optimised for fast writing - the reason is quite simple, the faster the disk spins the less time the laser has to penetrate the media and this can produce corrupt data - try using gold disks. Audio recording should always be restricted to x1.

Recording speed is a controversial issue with some users claiming the fastest speed possible should be used however, my experience agrees with Mitsumi and Philips, the slowest speed is the most reliable.

13: If you have two CD roms for copying one to the other, the read rom should be at least 32 speed or faster and run on the primary IDE port as a slave to the HDD. DO NOT put it on the secondary IDE port as a slave to the recording rom. Both read and write roms should be set at the same PIO mode setting of 3. It is also a good idea but not essential to have both read and write roms from the same manufacturer. This will make Windows 95/98 job easier when selecting drivers. ie one driver will run both roms. Roms of different makes might require two different drivers to be loaded and in some cases one of the drivers might have to be loaded from the autoexec.bat file, and this you don't want if it can be avoided.

Copying direct from one CD to another can produce intermittent transfer problems - it's always best to first copy files from the CD to a partition on your HDD that is not the partition in which your 'temp' recording directory is located, then copy them to the CD writer from there. When finished delete the files from your HDD. Also be aware that if you copy an audio CD directly to one of your own, the copying process first makes a wave file of each track and transfers that to your 'temp' directory, them transfers that wave file into an audio 'image' file and finally writes the digital audio data to the CD - it's a wonder it works at all!

Finally, Did you know that each time you record data to a CD it writes a 'lead in data file'. and this can be up to 13Mbs in size. This means if you write data 10 times to a CD you use up 130Mbs of CD space just writing lead in file instructions - thought that might interest you, just in case you wondered why your 650Mbs CD would only take 520Mhb of data files after 10 copying sessions!!

The fixes shown above are not a complete set, there are many more suggested by Mitsumi but those suggested above are the most likely to cure problems with every day DIY CD writing.

Other more complex No No's are - do not record directly across a Network - do not try to copy 0 bite files or files that are in use at the time of writing. - do not use 16bit (real mode) device drivers - if your PC is on a network log out if possible - SCSI controllers must be fully ASPI compliant - never try to copy from a compressed HDD or partition - if you are copying many small files make sure you write an ISO image file to your HDD and record no faster that x2 - and finally an odd one, do not use a HDD with 'Dumb' thermal re-calibration. You should only use a HDD with 'Smart' thermal re-calibration, ie it won't re calibrate if the CPU is being used!

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