The "V30" designation is critical. Inside the BIOS ROM, a version string reads something like "PSX ROM Version 3.0" (or 3.0J for Japan). Early PSX models had V1.x or V2.x BIOSes. The V30 (3.0) revision introduced:
Many Japanese-exclusive titles—which often pushed the console’s hardware limits—rely on specific calls within the v3.0J BIOS. Using this specific file ensures that timing-sensitive games run with frame-perfect accuracy. playstation scph5500 v30 japan bios scph5500bin top