Here is the complete Power-On Self-Test (POST) sequence for the Sony PlayStation (SCPH-5500, Japan, NTSC-J) using BIOS version SCPH5500.bin (v3.0) .
This process happens automatically when the console powers on, before the boot animation or any game loads.
1. Initial Hardware Power-Up & Reset
Voltage check: +3.5V, +5V, ±9V rails stabilize.
Master clock: 33.8688 MHz crystal oscillator starts.
Reset vector: CPU (R3000A) fetches initial PC (Program Counter) from 0xBFC00000 (BIOS ROM).
Cache disabled: Initial code runs from uncached, unmapped KSEG1 region.
2. CPU & System Core Initialization
Set Status register (SR):
Disable all interrupts.
Set boot exception vectors (BEV = 1 → use ROM vectors).
Isolate cache (ISC = 1, SWC = 1).
Set Cause register → clear pending exceptions.
Initialize COP0 (System Control Coprocessor). Playstation Scph-5500 -v3.0 Japan- Bios Scph5500.bin
3. RAM Detection & Test (simplified)
Main RAM: 2 MB (SCPH-5500 has no expansion RAM slot active yet).
Quick write/read test on first and last few bytes of each region.
Failure: Green screen (memory error) — solid, no further boot. Here is the complete Power-On Self-Test (POST) sequence
Scratchpad (1 KB) at 0x1F800000 – tested next.
Failure: Red screen.
Here is the complete Power-On Self-Test (POST) sequence for the Sony PlayStation (SCPH-5500, Japan, NTSC-J) using BIOS version SCPH5500.bin (v3.0) .
This process happens automatically when the console powers on, before the boot animation or any game loads.
1. Initial Hardware Power-Up & Reset
Voltage check: +3.5V, +5V, ±9V rails stabilize.
Master clock: 33.8688 MHz crystal oscillator starts.
Reset vector: CPU (R3000A) fetches initial PC (Program Counter) from 0xBFC00000 (BIOS ROM).
Cache disabled: Initial code runs from uncached, unmapped KSEG1 region.
2. CPU & System Core Initialization
Set Status register (SR):
Disable all interrupts.
Set boot exception vectors (BEV = 1 → use ROM vectors).
Isolate cache (ISC = 1, SWC = 1).
Set Cause register → clear pending exceptions.
Initialize COP0 (System Control Coprocessor).
3. RAM Detection & Test (simplified)
Main RAM: 2 MB (SCPH-5500 has no expansion RAM slot active yet).
Quick write/read test on first and last few bytes of each region.
Failure: Green screen (memory error) — solid, no further boot.
Scratchpad (1 KB) at 0x1F800000 – tested next.
Failure: Red screen.