Just like the Sega Saturn and other consoles that made the switch to the Compact Discs (CDs) format, PS1 games benefit from a new set of facilities: large storage (620 MB, in the case of the PS1), rich audio quality and a 'not-so-slow' read speed thanks to its 2x drive.
A typical PS1 game, shown with the disc flipped over. The underside of PS1 CDs feature a distinctive black coating that was once believed to prevent piracy. While technically incorrect - and I explain more in the 'Anti-piracy' section - I think it does provide a visual indicator of a genuine disc.
If you are curious about how Compact Discs (CDs) work, I've written a brief explanation in the Sega Saturn article. The PS1 also adopted the CD-ROM XA standard, but Sony leveraged this by combining game data with XA-ADPCM audio .
Be that as it may, PS1 revisions released up to 1997 (three years after the console's debut) were notorious for bundling a faulty CD drive laser , which resulted in frequent FMV and audio CD 'skips'. Later models fixed the laser unit and improved the housing, mitigating the problem.
Development ecosystem
Sony distributed an SDK to game studios comprising a C compiler and libraries. The latter were linked to BIOS routines for hardware access. As a side note, this level of abstraction later helped emulate the PS1 across a wide range of platforms - both official and unofficial.
Alongside the SDK, Sony also provided specialised hardware such as the DTL-H2000: a dual-slot ISA card containing the internals and I/O of the PS1 , plus extra circuitry for debugging purposes. The board could access the host's hard drive and execute PS1 software without restrictions. The accompanying software required a PC with Windows 3.1 or 95 installed.
A typical Net Yaroze setup, part of Christopher Rivett's collection .
Two years after the release of the PS1, Sony shipped a developer kit for hobbyists called Net Yaroze. In addition to the toolkit and manuals, it included a black-coloured PS1 console. The latter bundled a modified copy-protection system, allowing only Net Yaroze software to boot. The software was transferred from an external computer via the serial port and loaded into the PS1's main memory. The most significant limitation, when compared to studio-level devkits, was that the Net Yaroze did not provide access to the CD drive. This forced homebrew software to completely reside in main RAM (adding overhead).