Mainboard X9SCi-LN4F has blocked more IRQ for ethernet.
Supermicro isn't blocking anything. Interupts can be legacy or MSI(-X), either way there is nothing to block. I guess the ethernet controller runs in legacy mode, but consider that the 82574L controller has only 2 tx/rx queues, not a big deal.
Each additional packet, ethernet sends on another IRQ so that parallel processing is always optimal. It does not have multiple simultaneous sources. I use it for RouterOS (Mikrotik) and it works great if the motherboard manufacturer does not disable IRQ to more ethernet port (X9SCi-LN4F).
It looks like you don't have a real understanding of how packet processing works inside the kernel (but also outside, when bypassing it, as you do with netmap, dpdk, etc.), so I'm not going to waste time here (too long, too difficult), but in almost every scenario it is not possible to go parallel without having many different sources (and RSS, flow director/steering, etc.). Interrupt handling is a different story.
For this and other reasons I'm quite confident that low end low power e3 xeons will perform better than this Atom in many home/soho/appliace scenarios, benchmarks don't tell much about real world usage. Avoton seems to target very well the microcloud world but IMHO not so good the embedded-like world.
where are other ethernet? I watch only eth0.
Maybe are admin down?