A number of these units appeared on the secondary market (at generally high prices), and were popular because they would run games from any region and CD-R copies, which tended to result them in commanding high prices. All the blue units tend to have CD problems, but the DTL-H110x units (with an external PSU block) are significantly more reliable than the original DTL-H100x ones.
The installation of a modchip allowed the PlayStation's capabilities to be expanded, and several options were made available. By the end of the system's life cycle almost anyone with minimal soldering experience was able to realise the modification of the console. Such a modification allowed the playing of games from other regions, such as PAL titles on a NTSC console, or allowed the ability to play illicit copies of original games without restriction. Modchips allows the playing of games recorded on a regular CD-ROM. This created a wave of games developed without official approval using free GNU compiler tools, as well as the illegal reproduction of original discs. With the introduction of such devices the console was very attractive to Programmers and Pirates alike.
Individuals that insisted on creating copies of games that would play as their original counterparts faced many issues at the time, as the discs that were produced by Sony were designed to be difficult to copy - and impossible to copy on recordable media. Not only did the original discs have a specific black tint to them, they were mastered with a specific wobble in the leadin - when amplified and sliced this contained a 4 character sequence that was checked by the CD-ROM drives mechacon chip, and the drive would only accept the disk if it was correct (this string varied depending on the region of the disk - "SCEI" for NTSC:J machines, "SCEA" for NTSC:U/C machines, "SCEE" for PAL machines and "SCEW" for the Net Yaroze). Since the tracking pattern is pressed into the disc at the time of manufacture and CD-Rs have a clean spiral, this cannot be reproduced on a CD-ROM recorder. Some companies (notably Datel) did manage to produce discs that booted on unmodifed retail units, but this was beyond the average pirate. The other issue was that most PC drives used Mode 1 or Mode 2/Form 1 (2048 bytes/sector) and the PSX used a mixed-mode format with most data in Mode 2/Form 1 and streaming audio/video data in Mode 2/Form 2 - which a lot CD-R drives at the time could not handle well. Even after accurate copies were made, you still needed a modchip to send the correct code to the CD controller to enable the disc to be read (if a disk failed the security checks, it could be played as an audio CD, but the CD controller would reject any attempt at data transfers from it).
The creation and mass-production of these inexpensive modchips, coupled with their ease of installation, truly marked the beginning of console videogame piracy. Coincidentally, CD-ROM burners were made available around this time. Prior to the PlayStation, the reproduction of copyrighted material for gaming consoles was restricted to either enthusiasts with exceptional technical ability, or others that had access to CD manufacturers. With this console, amateurs could replicate anything Sony was producing for a mere fraction of the MSRP.