SafeDisc vs. SafeDisc 2: The Technique Explained
SafeDisc 2 was first encountered on the game â€˜Red Alert 2â€™ by Electronic Arts which caused a little shock in the back-up worldâ€¦ There were a lot of people who had problems copying this game while some seemed to copy it without any problems whatsoever. What was the deal here?
SafeDisc has a few hundred errors in the first 10.000 sectors of the disc but so does SafeDisc 2. The difference (and problem) lies in the first, what appear to be â€˜good,â€™ 500 sectors of the disc. The reading of the disc is not really a problem but when you want to write these sectors something goes wrong. We have to get a bit technical now but Iâ€™ll keep it simple so you can understand it:
The (estimated) first 500 sectors of a SafeDisc 2 protected game at first sight look like a collection of crappy data. It has a lot of zeroâ€™s but is also has special 10 sector groups containing a regular bit pattern. When you read this data with a CD-ROM it will pass through a so-called â€˜sector scramblerâ€™ which is present in all CD-ROMs and Writers. A regular pattern like this will â€˜appearâ€™: XYXYXYXYXYXYâ€¦
But, like I said, the problem occurs when you want to write these regular bit patterns because there are a lot of burners that donâ€™t like to do this. A writer has to produce the same patterns and it uses a so-called â€˜EFM Encoderâ€™ for this. When a regular bit pattern goes through the EFM Encoder it is converted to a smaller value by converting bits to bytes (8 bit = 1 byte) in a pre-determined way. Now hereâ€™s the problem: SafeDisc 2 tries to overload the EFM Encoder of the writer, by using the 10 sector groups, so it will loose synch and write wrong (irregular) bit patterns.
In short this is what happens when you write a SafeDisc 2 protected game. When you want to play a SafeDisc 2 back-up the game will check if there are regular bit patterns on the disc and if not it will give an error and refuse to play. We will call these sectors with regular bit patterns â€˜Weak Sectorsâ€™ from now on.
Some writers are more effected by the problem of writing regular bit patterns than others. Some writers (e.g. the Philips and Acer writers) have no problem at all copying these patterns while some simply canâ€™t do it (e.g. the Aopen and NEC writers). And then there are writers that will make a back-up that works in the recorder only like some Plextor models and Ricoh models. If you want to find out if your burner can handle SafeDisc 2 itâ€™s best to check the CloneCD Hardware Requirements and see if it supports â€˜Correct EFM encoding of regular bit patterns.â€™ This list doesnâ€™t mention writers that will make a back-up that works in the recorder only so hereâ€™s another list that doesâ€¦ http://www.geocities.com/pcp-freak/4cdfreaks/SafeDisc2.html