Short answer: OPL doesn't play PS1 games directly — it's built specifically for PS2 game ISOs. PS1 games on a PS2 run through the console's own built-in PS1 emulation, launched by a separate homebrew tool called POPStarter, which can run alongside OPL on the same setup.
Why Doesn't OPL Just Play PS1 Games Too?
OPL's entire design is built around loading PS2 disc images and presenting them to the PS2's hardware the way a real PS2 disc would. PS1 games need a completely different emulation layer, because the PS1 and PS2 have different underlying architectures — the PS2 can run PS1 software only because Sony built a dedicated PS1-compatibility component into the console's firmware, separate from how it runs native PS2 software.
POPS: The PS2's Built-In PS1 Emulator
POPS (PlayStation One emulation System) is the official component Sony built into the PS2 to run PS1 software — it's the same underlying technology used for Sony's own official "PS1 Classics" releases. Homebrew tools like POPStarter give you a way to launch POPS with your own PS1 game files, the same way OPL gives you a way to launch PS2 games without a disc.
Setting Up PS1 Games via POPStarter
- Obtain POPStarter (separate homebrew, not part of OPL) and install it to your memory card or USB drive alongside OPL.
- Convert your PS1 game files (from a disc you own) into VCD format — the format POPStarter expects, different from a standard PS1 ISO or BIN/CUE.
- Place the converted VCD files where POPStarter expects them (its own folder structure, separate from OPL's DVD/CD folders).
- Launch POPStarter from the FreeMCBoot menu (the same menu OPL launches from) to access your PS1 library.
OPL and POPStarter: Two Tools, One Memory Card
Because both are independent homebrew applications launched from the same FreeMCBoot menu, there's no conflict running both — you simply pick OPL for a PS2 game session or POPStarter for a PS1 game session. Neither interferes with the other's files or settings.
Setting up PS2 games with OPL?
Start with the full installation walkthrough.
How to Install OPL on PS2