Garry's Mod is a physics sandbox built on the Source engine where players spawn and manipulate props, NPCs, vehicles, and gadgets from Valve games to create contraptions or play community-created modes. Most players spend their time on multiplayer servers running DarkRP roleplay, Trouble in Terrorist Town, Prop Hunt, or Zombie Survival, while others build elaborate machines in single-player or create machinima. Because the game is almost entirely driven by user-generated content, performance depends far more on what you spawn than on any fixed game assets. The practical demands come from high prop and NPC counts, active physics constraints, Lua scripts, and constant syncing in multiplayer. These factors frequently cause stuttering or frame drops on older CPUs, especially when servers fill with player creations or you load dozens of Workshop addons. The 64-bit branch has improved multicore use, but many physics and entity calculations remain sensitive to single-thread speed. RAM usage climbs quickly with large collections of models and textures, and slow storage leads to painfully long map and addon load times. Common pain points include out-of-memory crashes in heavily modded sessions, hitches during big physics interactions, and choppy movement when servers get crowded. Understanding these realities helps avoid the frequent mistake of focusing only on GPU power. While rendering detailed mods can benefit from a decent graphics card, the real bottlenecks sit in the CPU, memory subsystem, and storage speed. A PC for Garry's Mod should therefore prioritize responsive physics, quick addon loading, and the ability to stay stable when dozens of custom entities are active at once.