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Regular & Irregular Bit Patterns

Mysteries Of The CDRW and Back Ups Revealed
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Much of a drive's success, or lack thereof, in making back ups of copy-protected discs can be traced to the drive's ability to correctly handle the RAW-DAO 96 'write' mode. RAW-DAO 96 = 2352 Bytes RAW Data + 96 Bytes P-W Subchannel Data is the best write mode for most programs that are used to make back ups. It allows writing of all subchannel information, including Digital Signatures, CD-Text, ISRC, Catalog Numbers, CD+G, CD+Midi, Gaps, Indices and Crazy TOCs. However, this is only part of the equation.

To make back ups of many CDs, the writer you choose will have to be able to write regular bit patterns, which means the writer has to produce the same patterns. It uses a so-called 'EFM Encoder' for this. Regular bit patterns go through the EFM Encoder and are converted to a smaller value by converting bits to Bytes (8 bit = 1 Byte) in a pre-determined way. Protection schemes such as Safedisc 2 operate by trying to overload the EFM Encoder of the writer using ten sector groups, which causes the CDRW drive to lose synch and write the wrong (irregular) bit patterns.

Even if the CDRW drive has robust and well-programmed firmware within it, this can still present a challenge for the drive. Although it can't be proven, there is a growing industry suspicion that numerous CDRW drive companies are working with copy protection providers to produce drives with firmware that are robust enough to handle most tasks, but not robust enough to handle these irregular bit patterns.

To further complicate matters, you must also have a drive that is able to extract (read) the CD in question correctly. In the read mode, you will need a drive that is able to read CDs in RAW+96 = 2352 Bytes RAW Data + 96 Bytes P-W Subchannel Data. This is the best mode for reading copy-protected discs for back up. In this mode, the drive is able to read all subchannel information like ISRC, catalog numbers, CD+G, CD+MIDI, gaps, indices, and digital signatures, which can be important in making a back up that will work.

Finding a drive that is able to do all of the above can be difficult, but it is necessary if you want to make accurate back ups that work. As you can see from the above information, it takes a very specific CDRW drive to perform all of these functions correctly.

The Contenders - Four CDRW Drives With Different Results

We wanted to select a variety of drives that covered a variety of price and performance levels. We did not select the drives based on any specific criteria, but instead chose four drives with a variety of speeds and performance levels for the test. We had extensive experience with two of the drives we chose, and the other two drives were newer to us.

Before we show you the results, we wanted to give you some basic background on each of the drives. In addition, we wanted to include a read test using Nero's CD Speed test. This benchmark should be used as an indication of the overall extraction performance of the drive, not as a determining factor in choosing a drive to handle your back up chores. Since the data on the protected CD has to be extracted in a RAW-style read mode, this test does give you a clear indication of what kind of extraction performance you can expect from each drive.

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