Original Playstation CD's have a black (actually dark blue) bottom as compared to normal (silver) pressed CD's and the gold/green/blue CD-R/CD-RW media's. This black color is not a copy protection but it will identify that it is a original PSX cd.

If someone is selling PSX CD's other then the black colored ones then they are illegal copies of the original game! The most common sold copies are called HKs (Hong Kong silvers), the have a silver bottom and are pressed in China.

• Bad Blocks
  The original PSX CD's are created with special recorders which are able to create bad blocks (segments of data on the CD which have been marked as invalid). These blocks normally are not wanted because any data that is located in a bad block is lost. Because of this, nearly all consumer CD recorders are designed to correct bad blocks when they read them before writing them to new CD's. Unless you work with Sony's special development recorders, (These recorders are only leased to companies that have a interest in keeping the protection intact, they are NOT available to end-users).
• Country-Code Lockout
  This protection prevents games from certain regions (US, JAP & PAL) to be played on playstations from a different region.
  The Country-Code Lockout protection compares the first 5 sectors on a CD with the PSX Country-Code. If these codes match the game will continue. This protection is used to discourage importing games.  Then using the below methods for copying WILL allow you to fully copy all data successfully onto a blank Cdr.

Usually the current available CD-R software is not able, using the default settings, to make a working backup.

To be able to play PSX backups the PSX needs to me changed so it will by-pass these protections. There are three ways to do this:

• Using the Swap-Trick by first booting with an original PSX CD and then replacing it with the backup. This ONLY works in the earlier versions of the Playstation.
• Install a MODified Boot Chip (ModChip) inside the Playstation (this can only be done by an experienced technician). The ModChip is a small electronic integrated circuit that "tricks" the PlayStation so it thinks the inserted CD contains the right Country-Code & Bad Blocks.
• Use a Cardridge (like the Game Enhancer) which plugs into the expansion slot. The advantage of this cartridge is that no modifications needs to be performed on the inside of the Playstation and it leaves the PSX warranty intact.

Advanced: Details on the actual Bad Blocks: (Written by Icepic)

Sectors 12 through 15 contain a zeroised EDC/ECC checksum (impossible) so if the PSX reads and doesn't see an invalid EDC/ECC then it knows that the CD in the drive is a copy. (The EDC is simply a CRC type hash that is used as a checksum to determine if the sector was read correctly. The ECC is used to recreate the sector data). The entire range of sectors is written in a RAW format (2352 bytes) and is completely zeroed, even the XA sub-header and EDC/ECC are zeroed. When it is copied on a CD-R, these sectors are exact, except for the EDC/ECC code that is (correctly) written as 0x3F13B0BC.

With a modified bios is should be possible to make an exact backup without the need to modify the Playstation. This way it would not automatically 'correct' what it thinks to be corrupt sectors with invalid EDC/ECC codes and using a copy method of writing the first track in RAW mode (2352 byte sectors, CD-DA) and then force the table of contents to report the track as a CD-XA track.