JS,
How did you "mod" your UEFI?
HS Port stands for HighSpeed Port? Then, did you disable from BIOS port 3 & 4?
I imagine this could be my problem ...

I cannot make my Seagate External Disc to work in USB3 SuperSpeed Mode ...
Did you meant that it should be under EHCI, to work for USB3 SSpeed?
I really appreciatte your help, this might be a tiny light at the end of this dark and bloody tunnel ... ;)
MauricioF,
Hey! Hopefully I can help you with this... Let me explain... First of all YES I did "Mod" my UEFI/BIOS... Now attempting to "Mod" any UEFI/BIOS IS VERY DANGEROUS & RISKY!!! In my case I have an AMI BIOS... There are tools available for modifying AMI
UEFI/BIOS... Can you tell me what UEFI/BIOS you have please... As well as your PC Specs please...
Second, Yes HS means Hi-Speed Port... You see xHCI (USB 3.0) Controllers are backward compatible with USB 2.0 (Hi-Speed) devices so xHCI topology INCLUDES 4 HS Ports that are PAIRED with the SS (SuperSpeed) Ports... For a total of 8 xHCI available ports...
So yes what I did was Disable xHCI HS Ports 3 & 4 in the BIOS... I recommend you download this tool: UsbTreeView... Here's the link:
http://www.uwe-sieber.de/files/UsbTreeView.zip With it you can see how your USB Controllers & Stack are set up...
Now, what are the specs for your external Seagate HDD? Is it USB 3.0? I think that in your case you have to Enable xHCI USB 3.0 in your BIOS... Set it to Enabled or Auto... And maybe Disable USB Legacy Support... In my BIOS I unlocked a EHCI Port Switching
function... That in some cases routes USB 3.0 devices to the EHCI Controller...
After you download and run UsbTreeView... Post a screenshot of your findings please... So I can see if I can and how to help you... ok... And Also please post screenshots of your UEFI/BIOS... Any areas that contain USB Settings ok... please...