Onboard NIC (intel) on Intel mainboard has RX drops problem.
RB-44GV NIC doesn't have problem with RX drops, but has problem with FCS/CRC error on Cisco switch. (tested with several cards)
RB-44G NIC has no problem with FCS/CRC but the RX drops exist.
Dlink 538T has problem with RX drops, but it much much lower than the others.
The RX drops problem only start when you have a lot of traffic, say above 45 Mbps, and a lot of rules (mangles/filters).
My test showed that without rules, just bandwidth test between core 2 PC & RB-450G, has no RX drops and bandwidth reach 500 Mbps.
I left my configuration with Dlink 538T (the best performance), 1700+ lines of mangle, 1300+ lines of queue tree, 20+ VLANs, 100+ Mbps bandwidth.
Dual Xeon 2.26GHz, 8 cores, 2 GB RAM, SATA DOM Level 6, ROS v4.9
CPU below 15%
RX drops still counting, but slower than before (using onboard NIC).
I wonder if I use "best of the best" NIC exists on the earth might solve this problem.
I sleep only 3 hours last two nights to figure out solving this problem, have no best answer yet.
Please anyone that have HUGE traffic on the Mikrotik box (as mine) please share here.
I still believe Mikrotik can handle this size of traffic.