First of all, thank you guys for your answers! I really apreciate it.
Try updating your network adapter's driver. Also check if other high-speed transfers (such as to another computer on your LAN) are affected.
1. I updated the drivers, but my motherboard is an H61, (MW-H61H2-M2 1.0) so, it's very old. I also had to update the bios firmware to make it work with my GPU (it worked!). I followed the procedures in their website: http://www.ecs.com.tw/ECSWebSite/Produc ... -Intel-RR-
I only used the CPU EVO to update to 8.1, there are still 2 bios updates: one for support to windows 8.1 and other to support intel 3rd gen cpus. I use windows 10 and 2nd gen CPU, I want to avoid updating the bios if possible because it's a risky procedure and may brick my PC; and there is no guarantee it will fix the issue because there is limited info on what the update does at the website.
2. I checked downloading on chrome using MEGA and they work fine, no lag at all even at twice the torrent speed. (torrents start to lag at 2MB/s)
I wonder if you've disabled your NIC's interrupt moderation feature (assuming it even has it). Lots of streams can really hurt crappy NIC drivers and they also typically peg a single core in Windows.
That's possible. I rechecked the CPU usage and it is only ~30%overall
; but core 0 is working at 100%
The system is freshly installed, maybe something went wrong somewhere? How to reenable this moderation feature to check it out?
Does changing the # of connections change anything?
It starts lagging with only 15 connections, it's hard to test because if I go lower it's hard to keep good transfer rates