Overclocking your Intel Core 2 Quad Q9550 on the ASUS P5Q Pro Turbo motherboard can significantly boost performance, but careful tuning is required to maintain stability and longevity.

1. Preparing Your System

• Cooling: Upgrade to an aftermarket cooler (e.g., Cooler Master Hyper 212 EVO) for better heat management.
• Power Supply: Ensure your PSU provides stable power for overclocking.
• BIOS Update: Update to the latest BIOS version for improved compatibility and stability.

2. Entering the BIOS & Initial Setup

• Restart and press “Delete” to enter BIOS.
• Load Optimized Defaults to start with a clean baseline.

3. Overclocking Steps

CPU Frequency Adjustments

• CPU Ratio: Keep it at 8.5 (max for Q9550).
• FSB Frequency: Increase from 333 MHz to 400 MHz to reach 3.4 GHz (8.5 × 400).
• CPU Voltage (VCore): Start with a slight increase (+0.05V) and test stability. Do not exceed 1.3625V.
• Memory Multiplier: Adjust to keep RAM within its rated speed as the FSB increases.

Additional Tweaks

• Load Line Calibration (LLC): Enable for stable voltage delivery.
• FSB Strap & Northbridge Voltage: Increase slightly if high FSB values cause instability.

4. Stability Testing & Monitoring

• Basic Boot Test: Check for immediate crashes or boot failures.
• Stress Testing: Run Prime95 or OCCT for several hours to check system stability.
• Temperature Monitoring: Use HWMonitor or Core Temp—keep temps below 70°C under load.

5. Fine-Tuning for Higher Clocks

• Increase the FSB in small steps beyond 400 MHz if stable.
• Some users have reached 4 GHz (471 MHz FSB) on similar setups with 1.31875V VCore (techenclave.com).
• The P5Q series struggles beyond 450 MHz FSB with quad-core CPUs (hardforum.com).

6. Final Recommendations

Patience is key—increase values gradually and test.
Backup important data before overclocking.
Keep voltage within safe limits to avoid long-term damage.

By following these steps, you can safely overclock your Q9550 on the P5Q Pro Turbo, unlocking improved performance while maintaining system stability.