The DXP4800+ throttles under sustained load because factory thermal paste covers only ~40% of the bare die, and BIOS fan curves are too conservative.
Fix: Repaste (spread technique) + aggressive BIOS SmartFan tuning. Full turbo, no throttling, 77-79°C sustained.
The 8505 is a bare die (no IHS). Dot/pea methods leave gaps. Spread a thin even layer across the entire die surface. Spread was 21°C cooler than pea method with the same paste (Arctic MX-6).
Enter BIOS: Ctrl+F12 at boot → Advanced → Hardware Monitor.
The key insight: BIOS SmartFan reads CPU temp directly, not the broken ACPI board temp sensor (~28°C always). Setting aggressive curves here is the correct fan control mechanism.
CPU SmartFan:
| Setting | Default | Recommended (Noctua NF-A14) |
|---|---|---|
| Fan PWM Slope | 20 | 8 |
| Fan Start PWM | 51 | 140 |
| Fan Off Temperature Limit | 0 | 0 |
| Fan Start Temperature | 45 | 40 |
| Fan Full Speed Temperature | 85 | 80 |
| Extra Temperature Setting | 70 | 60 |
| Extra Slope Setting | 80 | 12 |
SYS SmartFan1:
| Setting | Default | Recommended (Noctua NF-A14) |
|---|---|---|
| Fan PWM Slope | 35 | 4 |
| Fan Start PWM | 51 | 60 |
| Fan Off Temperature Limit | 0 | 0 |
| Fan Start Temperature | 25 | 30 |
| Fan Full Speed Temperature | 80 | 65 |
| Extra Temperature Setting | 70 | 50 |
| Extra Slope Setting | 80 | 8 |
The Extra Temperature and Extra Slope settings create a two-stage fan curve: gentle ramp below the Extra Temp (primary slope), steep ramp above it (extra slope). This eliminates fan hunting/oscillation. With the stock fan or without a Noctua, use higher Start PWM values (100+) and a slope of 10-15.
| Configuration | P-core | E-cores | Throttle? |
|---|---|---|---|
| Factory paste, stock BIOS | 100°C / 2.2 GHz | 100°C / 900 MHz | Yes |
| Factory paste, max fans | 100°C / 2.2 GHz | 100°C / 900 MHz | Yes -- paste is the bottleneck |
| Repaste (pea) | 100°C / 3.9 GHz | 83°C / 2.8 GHz | P-core at limit |
| Repaste (spread) + conservative curves | 85°C / 3.65 GHz | 77°C / 2.8 GHz | No |
| Repaste (spread) + aggressive curves (stock fan) | 77-79°C / 3.8 GHz | 63-70°C / 2.8 GHz | No |
| Repaste (spread) + Noctua NF-A14 + two-stage curves | 100°C / 3.7 GHz | 82-93°C / 2.8 GHz | No -- holds full turbo at thermal limit |
P-core hits 100°C during sustained single-core bursts (Cache Dirs scans) but holds 3.7 GHz via Intel thermal management -- no hard throttling. Idle: ~60-70°C. The Noctua is significantly quieter than the stock fan but can't dissipate 55W turbo burst heat as fast. The CPU manages itself at 100°C without performance loss.
- Factory paste only contacts ~40% of the die. The paste isn't dried out -- it's just poorly applied (too little, uneven).
- ACPI firmware defect -- fan cooling devices are bound to board temp (~28°C), not CPU temp. Kernel fan control never kicks in.
- Conservative stock BIOS curves -- even the BIOS SmartFan defaults don't ramp fans fast enough for burst loads.
The heatsink base is flat. Poor thermal contact is entirely a paste application issue.
- UGOS isn't affected. It has its own fan daemon (
hwmonitor) that bypasses the broken ACPI binding. - The IT8613E Super IO chip exists at ISA
0x0a30. The ich777/unraid-it87-driver plugin exposes fan RPM monitoring if you want it. - ACPI fan cooling devices (
cooling_device6-10) are virtual and toggling them has no effect on physical fans. Don't waste time with ACPI fan scripts. - The Unraid Dynamix Cache Dirs plugin runs
findscans every ~10 min that spike one P-core to 100% for 30-60s. This is the primary heat source on an otherwise idle NAS. - Tested on DXP4800+ (Intel Pentium Gold 8505) with Unraid 7.2.4.