The original Garry’s Mod relies entirely on Valve’s Source Engine, DirectX, and heavy CPU physics calculations to render, simulate, and manipulate objects. The PSP, released in 2004, features a 333MHz processor and a meager 32MB of RAM (64MB on later models). It is physically incapable of running the PC version of GMod.
Have you modded your PSP? Or sticking to the classic way of playing gmod psp better
By following these tips and tricks, you'll be well on your way to enjoying the best that Gmod PSP has to offer. The original Garry’s Mod relies entirely on Valve’s
As one developer succinctly put it on a PSP engine forum, working within the PSP's "strict limits and getting the most out of your work is 90% of the fun." But even with that can-do spirit, "porting the Source engine to PSP is insanity in itself". Simply put, the native hardware is fundamentally incompatible. Have you modded your PSP
Other developers created 2D sidescrolling or top-down sandboxes written in Lua (via the PSP Lua Player). These allowed players to drop physics objects, wire them together, and trigger explosions, mimicking the mechanical creativity of GMod's "Wiremod" on a miniature scale. How to Experience GMod on PSP Today