Je vous rassure, ce n'est pas la présence ou l'absence d'ECC sur votre système qui vous empêche de tirer plus de 40Mbit/s.
40Mbit/s c'est ridicule.
Un pauvre petit boitier Alix 2D13 sait tenir du 80mb/s avec même pas 500 Mhz.
Pour moi votre problème ne se situe pas au niveau du CPU. C'est quoi les cartes réseau ?
Je vous renvoi à ce lien https://www.pfsense.org/hardware/
10-20 Mbps
We recommend a modern (less than 4 year old) Intel or AMD CPU clocked at at least 500MHz.
21-100 Mbps
We recommend a modern 1.0 GHz Intel or AMD CPU
101-500 Mbps
Server class hardware with PCI-e network adapters, or newer desktop hardware with PCI-e network adapters. No less than a modern Intel or AMD CPU clocked at 2.0 GHz.
Network Card Selection
Selection of network cards (NICs) is often the single most important performance factor in your setup. Inexpensive NICs can saturate your CPU with interrupt handling, causing missed packets and your CPU to be the bottleneck. A quality NIC can substantially increase system throughput. When using pfSense software to protect your wireless network or segment multiple LAN segments, throughput between interfaces becomes more important than throughput to the WAN interface(s).
NICs based on Intel chipsets tend to be the best performing and most reliable when used with pfSense software. By comparison Realtek chipsets perform quite poorly. We therefore strongly recommend purchasing Intel cards, or systems with built-in Intel NICs up to 1Gbps. Above 1Gbps, other factors, and other NIC vendors dominate performance.